Digestive System.

Digestive System

SALIVARY GLANDS Produce saliva Names of some salivary glands:
Parotid (largest). Mumps is a virus that attacks here. Submandibular Sublingual Functions of salivary glands To moisten food so you can swallow, especially crackers. The mucus in the saliva is what moistens the food. To inhibit growth of bacteria (which like dark, warm, moist areas). What does this are the antibodies, enzymes, and macrophages in the saliva.

STRUCTURE OF TOOTH GINGIVA are the gums
CROWN is the area above the gingiva ROOT is embedded in a socket in the bone. In the maxilla, the root can extend into the maxillary sinus. Damage to the sinus can be a lot of problems. ENAMEL is the external layer of the tooth. It is stronger than bone, but does wear out. It is suppose to be ivory color, not white. Whitening procedures scrape away outer oxidized layer, to expose the layer underneath, which is white, but it will oxidize, too. DENTIN is deep to the enamel. It is like bone, with living tissues and cells. PULP CAVITY with PULP is deep to the dentin. It has blood vessels and nerves. PERIODONTAL LIGAMENT attaches the tooth to the bone. It’s like periosteum. Disease of this structure is the most common cause of tooth loss in adults.

Tooth Structure Figure 22.11

Tooth Problems When bacteria eat away at the enamel, what’s it called? CAVITY The dentist removes a larger area where the bacteria are, and fills it in. If the cavity extends into the pulp cavity, there is no way to clean it up. The treatment is to make a big hole, scrape out the pulp, and fill up the whole thing = ROOT CANAL. This is a dead tooth, but still there. Bacteria between the gingiva and tooth causes inflammation of the gingiva = GINGIVITIS. When it gets worse, the gingiva pulls away from the tooth and the bacteria extends down to the periodontal ligament = PERIODONTITIS. This is the major cause of tooth loss. The tooth loosens and falls out. That’s why you need to floss.

Layers of GI Tube There are four layers:
1. MUCOSA (inner layer). The lining varies from region to region. Epithelium Lamina Propria: Loose connective tissue Muscularis mucosae: very thin smooth muscle, causes little twitches within the mucosa. 2. SUBMUCOSA (moderate dense connective tissue). Lots of elastic fibers, blood vessels, and lymphatic vessels. 3. MUSCULARIS EXTERNA (smooth muscle layer with two parts: Circular Layer (inner) Longitudinal layer (outer) 4. Serosa

Serosa Mucosa Muscularis Externa Submucosa

3. Muscularis Externa Muscularis Externa is extremely important for digestion. It allows for 2 types of actions: a. PERISTALSIS: a rhythmic contraction to push something along. This pushes food down by smooth muscle contraction. b. SEGMENTATION: A back-and-forth squeezing of the muscle to grind up food. Food moves forward then backward a little, then forward again. Function is to churn up the food inside. Some areas have thicker smooth muscle = SPHINCTER. Circular muscles open and closes an opening. Controls the flow of food from one region to another.

Layers of GI Tube 4. SEROSA is not in all regions (none in esophagus).
Simple squamous epithelium Loose connective tissue From internal to external, the layers of this tube are the mucosa, submucosa, muscularis, serosa.

Esophagus Extends from the oropharynx to the stomach, about 25 cm long. The things that are specialized in the esophagus are: 1. MUCOSAL EPITHELIUM (non-keratinized stratified squamous epithelium). Why? It protects against things you swallow; pointy potato chips, etc. Cuboidal would slough. 2. MUSCULARIS EXTERNUM in upper half = skeletal muscle. Lower half = smooth muscle. Why? The upper half, skeletal muscle, is under voluntary control. Smooth muscle is not voluntary. Food gets caught in the lower half because it hasn’t started peristalsis.

Cardiac Sphincter The esophagus goes through the thoracic cavity.
It needs to go through the diaphragm’s opening (esophageal hiatus). It empties to the stomach through a CARDIAC SPHINCTER = a thickening of the muscularis externa. This is NOT A TRUE SPHINCTER.

Stomach Anatomy

Stomach: Functions Store Food
Mechanically churns food into a paste called CHYME Kill bacteria Some digestion: of proteins Some absorption: of water, alcohol Gastric emptying is the release of food from the stomach into the duodenum; the process is tightly controlled with liquids being emptied much more quickly than solids.

STOMACH FUNCTIONS 1. Store Food, so it can be slowly released into a small intestine. Your whole Thanksgiving dinner can take your stomach diameter from 2” to 8” diameter. 2. Mechanically Churns food. Secretions from the stomach is added, turns everything into a gooey paste. When you throw up, you can see the enzyme secretions = CHYME. 3. Kill bacteria. The stomach is very acidic (pH 1) like battery acid. Chyme will even eat through clothing. 4. Some digestion: of proteins. 5. Some absorption: of water, alcohol (alcohol is absorbed in the mouth, too!) Food takes four hours to completely leave the stomach.

The Stomach Figure 22.15a-c

Stomach Cells PARIETAL CELLS in the stomach secrete hydrochloric acid and digestive enzymes which kill bacteria in the stomach. They also secrete intrinsic factor, which is needed to absorb vitamin B12. CHIEF CELLS secrete an enzyme called pepsinogen. When pepsinogen is exposed to hydrochloric acid (HCl), it is cleaved into pepsin, its active form. Pepsin digests proteins.

Intrinsic Factor The parietal cells in the stomach secrete a substance called INTRINSIC FACTOR. Vitamin B12 requires intrinsic factor in order to be absorbed. A person who lacks intrinsic factor (such as those who have a stomach stapling procedure or gastric bypass) will not be able to absorb vitamin B12 and they will get a type of anemia called pernicious anemia. Treatment is injectable B12 shots monthly for the rest of their lives.

Gastric gland Figure 22.15a-c

Two major causes of Peptic Ulcers:
1) 60% of gastric and up to 90% of duodenal ulcers are due to a bacterium called Helicobacter pylori. The body responds by increasing gastrin secretion, which erodes the stomach lining. 2) NSAIDs (non-steroidal anti-inflammatory drugs, such as aspirin) block prostaglandin synthesis. Prostaglandins promote the inflammatory reaction. They also are found in the stomach, protecting it from erosion.

Problems With the Stomach
The cardiac sphincter doesn’t close well, since it is not a true sphincter; consequences: You can throw up (reverse peristalsis). Rats do have a true cardiac sphincter, and can’t vomit! That’s why rat poison won’t kill people or dogs; they can throw it up. Another consequence: hiatal hernia.

HIATAL HERNIA Part of the stomach, protrudes through esophageal hiatus, causing pain and difficulty swallowing. It is the most common of all hernias. There is a great amount of acid reflux; erodes walls of esophagus, causing ulcerations of esophagus. Treatment is surgical; pull down the stomach, and tighten the hernia in a laparoscopic procedure.

The Small Intestine Crypt of Lieberkuhn Figure 22.17a-c

Small Intestine Regions
Duodenum “12 finger widths long” Jejunum “hungry when empty” Ileum “twisted”

DUODENUM This is the shortest region, only one foot long.
It receives chyme from the stomach. This is where digestion begins. There are two ducts at the beginning of the duodenum from the pancreas and gallbladder. It is the site of action of liver secretions (bile) and pancreas secretions (digestive enzymes and bicarbonate).

Pancreas PANCREAS is an endocrine gland, and also participates in digestion. Most of the digestive enzymes are made here. They go out the PANCREATIC DUCT to enter the small intestine. It also produces BICARBONATE (from a hormone called SECRETIN) to increase the pH (decrease the acidity) of the chyme coming from the stomach. If there is too much acid there, get a DUODENAL ULCER.

PANCREAS ACINAR CELLS: secretes digestive enzymes
ISLETS OF LANGERHANS: secretes insulin and glucagon

Pancreas Acinar cells (secrete enzymes)
Islet of Langerhans (secretes insulin and glucagon)

GALL BLADDER This is located inferior to the liver, and its function is to store and concentrate bile. Bile is a detergent/soap (not an enzyme) which emulsifies fat: It breaks down the fat into microscopic droplets which can be broken down by pancreatic enzymes. It does NOT make or secrete bile; that is done by the liver. Bile is made in the liver from Hemoglobin (Hgb), and also contains cholesterol and other things. The function of bile is to break down lipids (fats) so they can be digested.

Jejunum JEJUNUM (“empty”)
This is the part of the small intestine where most digestion and absorption occurs. It is 3 feet long.

Ileum ILEUM (“twisted”) is feet long. It is the terminal portion of the small intestine. Much of the absorption takes place here.

Crypt of Lieberkuhn Lacteal

Crypt of Lieberkuhn Figure 22.17a-c

Absorption in Small Intestine
In the villis is a fenestrated capillary bed, which needs to absorb a lot of material. The small intestine absorbs carbohydrates, fats, and proteins (although protein enzymes have already begun working earlier in the digestive tract in the stomach). The walls of the small intestine secrete most of the digestive enzymes that are active in its lumen.

Lymphatics of Small Intestine
There are also large lymphatic capillaries in each villis called LACTEALS, whose function is to absorb breakdown products of fat. The vessel is large so it won’t get clogged up. Under all this are the MUSCULARIS MUCOSA muscles which can twitch to move the villa so food does not get stuck.

Problem with Small Intestine
Crohn’s Disease Autoimmune disease of the GI tract Most common area affected is small intestine Celiac disease (Sprue; gluten intolerance)

Large Intestine (Colon, or large bowel)
This is about 5 feet long, diameter of 4”. Absorbs a LOT of water and salts Absorbs electrolytes (Na, K, etc) Stores feces for defecation (terminal portion) Contains abundant bacteria (E. coli): Make vitamins (B5, K, biotin) Allow material to move through large intestine easier Keep out harmful bacteria They eat things you can’t digest Fiber Some sugars that we don’t have enzymes for

Regions of the Large Intestine
Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anus

Large Intestine Figure 22.18a

Problems with Large Intestine
DIVERTICULITITS INFLAMMATORY BOWEL DISEASE Crohn’s Disease Ulcerative colitis IRRITABLE BOWEL SYNDROME COLON CANCER SIGMOIDOSCOPY or a COLONOSCOPY POLYPS HEMORRHOIDS

DIVERTICULITITS DIVERTICULUM (Diverticula is plural) can form, a small pouch in the large intestine. They can become inflamed, usually from a small, hard piece of feces, causes the condition known as DIVERTICULITITS. These are painful and often need to be surgically removed. May be caused by lack of fiber, causing increased pressure in the colon.

Inflammatory Bowel Disease (IBD)
IBD is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis

IRRITABLE BOWEL SYNDROME (IBS)
IBS is a diagnosis of exclusion. Symptoms are chronic abdominal pain, bloating, and alteration of bowel habits in the absence of any detectable organic cause. May manifest as diarrhea or constipation or may alternate between the two. May be caused by infection, stress, or onset of maturity No cure; treatments attempt to relieve symptoms, including dietary adjustments, medication and psychological interventions.

COLON CANCER This is the #1 most deadly cancer (kills more people) because it metastasizes and there are no symptoms. It can be diagnosed by seeing blood in the stool; this is an easy test, but not very accurate. A more accurate test is a SIGMOIDOSCOPY. A tube is inserted into the sigmoid colon, done in the doctor’s office. The tube has a light, and they look for growths on the walls of the intestine = POLYPS, which are pre-cancerous growths. A colonoscopy is done under general anesthesia since the tube has to go through the entire colon, but it’s more effective.

Hepatic Portal System Almost all of the blood coming from the digestive system drains into a special venous circulation called the portal circulation. Before these absorbed substances can go into the systemic circulation (the main blood circulation in the body), it must be filtered first to remove or detoxify toxic substances first. This filtering and detoxification is one of the 500+ functions of the liver.

Liver Makes blood Makes blood proteins (clotting factors) Makes bile
Regulates glucose levels Processes fats Makes cholesterol Processes amino acids Detoxifies chemicals

Liver Hepatic Triad: Vein, Artery, Bile Duct Figure 22.23a, c, d

Liver: sinusoids and hepatocytes

Blood Flow in the Liver Blood flow to the liver is unique in that it receives both oxygenated and deoxygenated blood. Nutrient-rich, oxygen-poor blood from the intestine enters the liver by the hepatic portal vein. It flows through the sinusoids for detoxification. Oxygen-rich blood enters the liver by the hepatic artery. It flows through the sinusoids to supply them with oxygen. All of the blood mixes together, and when the oxygen demand of the hepatocytes is satisfied, and the toxins have been removed, the oxygen-depleted blood collects in a central vein within each lobule, which drains into the hepatic vein. The hepatic vein subsequently drains into the inferior vena cava and back to the heart.

Function of Hepatocytes
Detoxification of poisons Picking up and processing of nutrients from the portal blood This includes picking up glucose from the nutrient-rich blood coming from the small intestine and stores it as glycogen (the storage form of glucose) for when the body needs it later. Storage of some vitamins

Kupffer Cells Within the sinusoids are KUPFFER CELLS, which are macrophages. As blood flows through the sinusoids, they phagocytize old erythrocytes. The released Hgb is given to the hepatocytes, which convert it to bilirubin, one of the main components of BILE. Bile flows through a series of channels called the BILE CANNICULI to the bile duct.

Problems with the Liver
HEPATITIS CIRRHOSIS JAUNDICE

Liver Problems Infection of the liver = HEPATITIS (can be deadly)
CIRRHOSIS is when the hepatocytes die and are replaced by connective tissue. This is often from alcoholism, which kills the hepatocytes.

Jaundice One of the symptoms from any liver disorder is a connection of the bile canaliculi and the sinusoid so some bilirubin can enter the blood. Bilirubin is yellow-green (later in its degradation it will turn brown and that is what gives the feces its color). The yellow color of bilirubin in the skin is known as JAUNDICE.

GREATER OMENTUM GREATER OMENTUM is flat, and is in front of the intestines like an apron. Its function is to store fat, especially in men.

Part 1: Metabolic Pathways Part 2: GI Physiology

Simple and Complex Carbohydrates
There are three main simple sugars (AKA monosaccharides or simple carbohydrates) Glucose Fructose Galactose If you join a glucose to any of these, you get a disaccharide Glucose + Glucose = Maltose Glucose + Galactose = Lactose Glucose + Fructose = Sucrose

Simple and Complex Carbohydrates
If you join many monosaccharides and/or disaccharides together, it is called a polysaccharide (AKA complex carbohydrate). These are stored in the liver as glycogen. They can be broken down later into glucose as needed. The storage form in plants is called starch. When we eat starch, we covert it to glycogen and then store it.

Glucagon and Insulin Glucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar (glucose) levels fall too low. Glucagon causes the liver to beak down the stored glycogen into glucose, which is released into the bloodstream. Since glycogen is being broken down, this process is called glycogenolysis. Don’t confuse this with glycolysis (break down of glucose to ATP)! High blood glucose levels stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels at a stable level.

Glycolysis Glycolysis is the process where cells take in glucose and break it down into pyruvate, and ATP is released. This is how we get ATP from glucose. Fructose and galactose can also be broken down into pyruvate and ATP. During glycolysis, NAD (an energy molecule) is reduced to NADH. If you run out of NAD, glycolysis will stop. Therefore, we need to oxidize NADH to convert it back into NAD. This can be done by aerobic or anaerobic respiration, or fermentation.

Aerobic vs. Anaerobic Respiration
(in the mitochondria)will result in 6 ATP’s. Anaerobic respiration (in our cytoplasm) will result in only 2 ATP’s. More importantly, we get our NAD back, so glycolysis can continue.

Making ATP by Aerobic Respiration
Takes place in the mitochondria Requires oxygen Breaks down glucose to produce ATP Waste products are CO2 and H2O (we exhale them) The good thing about making ATP from our mitochondria is that we can make a LOT of it. The bad things are that it takes longer to make it, and it requires oxygen, and a muscle cell may have used up all the oxygen during a sprinting run.

Making ATP by Anaerobic Respiration
Takes place in the cytoplasm Does not require oxygen Breaks down glucose to produce ATP Waste product is lactic acid The good thing about making ATP this way is that we can make it FAST. The bad thing is that it does not make much ATP, and we deplete the reserves quickly.

Lactic Acid Build-up During strenuous workouts where oxygen becomes deficient, the pyruvate product of glycolysis does not have enough oxygen to use for aerobic respiration, so it has to undergo anaerobic respiration. The enzyme lactate dehydrogenase (LDH) is used to transfer hydrogen from the NADH molecule to the pyruvate molecule. Pyruvate with the extra hydrogen is called lactate. Lactic acid is formed from lactate. This causes muscle aches and fatigue. Lactic acid is deactivated by the addition of oxygen to it. Therefore, breathing heavily adds the oxygen to our system to deactivate lactic acid, and the muscle pains go away. Warm water or ultrasound will also increase oxygenated blood to the muscles, easing muscle cramps from lactic acid.

ATP and Creatinine Phosphate
What do we do when we run out of ATP? Muscle fibers cannot stockpile ATP in preparation for future periods of activity. However, they can store another high energy molecule called creatinine phosphate. Creatine phosphate is made from the excess ATP that we accumulate when we are resting. During short periods of intense exercise, the small reserves of ATP existing in a cell are used first. Then creatinine phosphate is broken down to produce ATP.

Aerobic vs. Anaerobic Respiration
When do we use aerobic respiration? Resting (can breathe easily) Running marathons (can breathe easily on long runs) Marathon runners want to make sure there will be enough readily available energy for the muscles, so they eat a lot of carbohydrates over a two-day period before the marathon. That’s why they load up on pasta before a marathon. When do we use anaerobic respiration? Sprint running (can’t talk while sprinting!)

Gluconeogenesis Gluconeogenesis is a metabolic pathway that results in the generation of new glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and amino acids. Therefore, if we do not have enough glucose in our body, we will break down proteins (muscles) to make glucose. It is one of the two main mechanisms to keep blood glucose levels from dropping too low (hypoglycemia). The other means of maintaining blood glucose levels is through the degradation of glycogen (glycogenolysis).

Part 2 GI Physiology Welcome to your articulate file for the Digestive system –or alimentary tract. The alimentary tract begins with the oral cavity, continues into the oropharynx and laryngopharynx to the esophagus, to the stomach, to the small intestine with its three parts (duodenum, jejunum, and ileum—I remember this as “Down Jones Industrial” finally the ingested contents travel through the one-way ileocecal valve and enter the large intestine leading to the rectum and anus. Many accessory digestive organs are passed along the way: such as the pancreas, liver, and gallbladder. The alimentary tract provides the body with continual supply of water, electrolytes, and nutrients. This requires (1) movement of food through the alimentary tract; (2) secretion of digestive juices and digestion of food; (3) absorption of digestive products, water, and various electrolytes; (4) circulation of blood to carry away absorbed substances; and (5) nervous and hormonal control of all these functions. I will be discussing the basic principles and function of the entire alimentary tract during this lecture Figure 62-1; Guyton & Hall

Saliva The saliva serves to clean the oral cavity and moisten the food. It also contains digestive enzymes such as salivary amylase, which aids in the chemical breakdown of polysaccharides such as starch into disaccharides such as maltose. It also contains mucus, a glycoprotein which helps soften the food and form it into a bolus.

Stomach The stomach is responsible for the digestion of protein and ionization of minerals. Mucous cells (in the stomach) secrete mucous. The pancreas secretes bicarbonate. Mucous, bicarbonate, and prostaglandins protect the stomach lining from being digested. The parietal cells of the stomach secrete hydrochloric acid (gastric acid) and intrinsic factor. Hydrochloric acid (HCl), along with pepsin (from the chief cells), breaks down proteins to their individual amino acids.

Stomach Protection and Damage
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Stomach Acid The acid itself does not break down food molecules.
It provides an optimum pH for the activation of pepsin, and kills many microorganisms that are ingested with the food. It can also denature proteins. The parietal cells of the stomach also secrete a glycoprotein called intrinsic factor, which enables the absorption of vitamin B-12.

Stomach Acid Diseases Hypochlorhydria Hyperchlorhydria

Small Intestine Duodenum Absorption of minerals
Receives pancreatic digestive enzymes Secretes hormones when acidic chyme enters duodenum Secretin Tells pancreas to secrete bicarbonate Tells liver to make bile Cholecystokinin (CCK) Tells pancreas to release protein-digesting enzymes Tells the gallbladder to release stored bile. Therefore, it stimulates digestion of fat and protein. GIP stimulates insulin secretion Motilin Initiates peristalsis (increases GI motility) Tells the Chief cells to secrete pepsinogen Secretes enzymes to break down polysaccharides Maltase: breaks maltose down into glucose Lactase: breaks lactose down to galactose plus glucose Sucrase: breaks sucrose down into fructose plus glucose

Small Intestine Duodenum
When there is no more chyme entering the duodenum, it secretes glucose-dependent insulinotropic peptide (GIP). GIP is synthesized by K cells, which are found in the duodenum and jejunum. GIP stimulates insulin secretion. Insulin is in the blood stream. It takes the absorbed sugars and pulls them into cells that need it. GIP also stimulates lipoprotein lipase activity in adipocytes. This causes fat to be broken down into fatty acids.

Lipid digestion and absorption
Lipid digestion utilizes lingual and pancreatic lipases, to release fatty acids and monoglycerides. Bile salts improve chemical digestion by emulsifying lipid drops Lipid-bile salt complexes called micelles are formed I’d like to start the discussion of this slide with addressing the role of bile salts. Simply put, bile salts form micelles, which are small spherical cylindrical globules– shown here as the small structures at the bottom of the picture. These develop because each bile salt molecule has a fat-loving sterol group (i.e., it is hydrophobic) and a water loving group (hydrophilic) The fat loving portion surrounds a portion of the ingested fat globule and the water-loving portions will project outward to cover the surface of the micelle. Because these polar groups are negatively charged, they allow the entire micelle globule to dissolve in the water of the digestive fluids in the small intestine and remain in solution until the fat is digested and the fatty acids absorbed in the blood. The micelles are important for ferrying the resulting fatty acids and monoglycerides to the brush border, and once the fats are absorbed by the blood then the bile salts can be reused to ferry more digested fats to the brush border. So, once the bile salts form micelles of fat droplets, the cholesterol esters and phospholipids we consumed in our diet are broken down by cholesterol esterase and phospholipase, respectively. These enzymes release free cholesterol and fatty acids. I will leave this slide with a stern caution: bile salts from the liver and gallbladder do NOT DIGEST INGESTED FATS! Rather, they only emulsify the fats—packaging into smaller portions to increase the surface area so that the lipases have an easier time digesting the fats.

Fatty Acid Absorption Fatty acids and monoglycerides enter intestinal cells via diffusion; bile salts can be reused to ferry more monoglycerides They are combined with proteins within the cells Resulting chylomicrons are extruded They enter lacteals and are transported to the circulation via lymph As I said in the previous slide, the bile salt micelles transport monoglycerides and fatty acids to the brush border. The digested fats diffuse into the epithelial cells. The fatty acids are used to form triglycerides and combine with proteins to form chylomicrons. Chylomicrons then transport the phospholipids to the underlying lacteal vessel which then transports the chylomicrons back to the circulating venous blood. The half life of a chylomicron is about 1 hour and most of the chylomicrons are removed from the circulating blood as they pass through the capillaries of adipose tissue or the liver. Adipose tissue and liver both contain large quantities of the enzyme lipoprotein lipase. Once the free fatty acids cross the cell membrane, they are resynthesized into triglycerides so they can be stored in the cells. If free fatty acids need to be released from storage cells like adipocytes, then the triglycerides are hydrolyzed into free fatty acids and glycerol (we will discuss hydrolysis during your metabolism lecture). And free fatty acids are transported by albumin for the body’s energy needs. In the post-absorptive state, the lipids are then transported in plasma in the form of lipoprotein. You’ve heard of “good cholesterol” and bad cholesterol. These terms are really referring to lipoproteins. HDL stands for high density lipoprotein and it is high density because there is mostly protein in this molecule and fewer fats. LDL stands for low density lipoprotein and this molecule has many more fats transported within it—hence the term “bad cholesterol.” The LDL transport triglycerides synthesized by the liver mainly to adipose tissue, whereas the HDL are important for the different stages of phospholipid and cholesterol transport from the liver to the peripheral tissues or from the peripheral tissues back to the liver. I always remember that HDL is the “good cholesterol” for two reasons: It contains more protein than fat and the fats being transported are either going to be used by the cells of the body for energy or removed from the body by the liver and expelled into the GI tract. LDL is “bad cholesterol” because it contains mostly fats and is merely transporting them to adipocytes for storage. Thus, we want a greater HDL to LDL ratio. Having a high HDL to LDL ratio also prevents atherosclerosis. Atherosclerosis is a disease of the large and intermediate-sized arteries in which fatty lesions or plaques, develop on the inside surfaces of the arterial walls. So how can you help your body excrete more fats? Eat more fiber. Remember the fiber is going to keep the fats soluble in the GI tract and makes it easier to defecate. IF you have pure fats being excreted from the GI tract this is called steatorrhea, an unpleasant fatty diarrhea.

Small Intestine Jejunum
Absorbs water-soluble vitamins, protein and carbohydrates. The proteins began to be broken down into amino acids in the stomach by pepsin and acid. Proteins are further broken down into amino acids in the duodenum by trypsin and chymotrypsin (made by the pancreas and secreted into the duodenum). The carbohydrates are broken down in the duodenum by enzymes from the pancreas and liver into sugars.

Small Intestine Ileum Absorbs fat-soluble vitamins, fat, cholesterol, and bile salts. Fats are broken down into fatty acids in the duodenum. First, bile emulsifies the fat (breaks it down into droplets). Then, lipase (made in the pancreas) breaks the fat into fatty acids, which are small enough to be absorbed.

Pancreas Enzymes Lipases Amylases Proteases
The pancreas secretes about one and a half liters of pancreatic juice a day! Pancreatic juice secretion is regulated by the hormones secretin and cholecystokinin, which is produced by the walls of the duodenum upon detection of acid food, proteins and fats. The enzymes produced by the pancreas include Lipases Amylases Proteases

Pancreas Enzymes Lipases Amylases Proteases
Digestion of fats, oils, and fat-soluble vitamins Amylases Break down starch molecules into smaller sugars. Break down carbohydrates into maltose Proteases Break down protein into smaller amino acids Proteases include trypsin, chromotrypsin and carboxypeptidase. Proteases are also responsible for keeping the small intestine free from parasites (intestinal worms, yeast overgrowth and bacteria). A lack of proteases can cause incomplete digestion that can lead to allergies and the formation of toxins.

Regulation of Pancreatic Secretion
Secretin and CCK are released when fatty or acidic chyme enters the duodenum CCK and secretin enter the bloodstream Upon reaching the pancreas: CCK induces the secretion of enzyme-rich pancreatic juice Secretin causes secretion of bicarbonate-rich pancreatic juice Vagal stimulation also causes release of pancreatic juice I want to go over again the control over the exocrine function of the pancreas. When fatty or acidic chyme from the stomach arrives in the duodenum, hormones released from the intestinal gland will signal the pancreas to release its secretions. Secretin stimulates the pancreas to release the bicarbonate rich pancreatic juice to neutralize the stomach acids. Cholecystokinin will stimulate the pancreas to release its digestive enzymes that can digest lipids, nucleic acids, carbohydrates and proteins. In addition to this hormonal control over the pancreas, stimulation of the parasympathetic system can also cause the pancreas to release its secretions. This parasympathetic stimulus would be conveyed through the Vagus nerve (or Cranial nerve number 10) and its interesting how the stimulus arrives. The vagus nerve actually carries impulses to the digestive tract starting with the moment you see or even think about food. For example, 30% of the response to a meal is initiated by the anticipation of eating and the odor and taste of food. The vagus carries impulses to the stomach and GI tract and stimulates them—the stomach starts to secrete HCl. The gastric phase accounts for 60% of the acid response to a meal. It is initiated by distention of the stomach which leads to nervous stimulation of gastric secretion. During these first two phases, the vagus nerve is also transmitting stimuli to the pancreas and the pancreas is starting to secrete bicarbonate juices and enzymatic secretions in anticipation of chyme arriving soon. Then, the intestinal phase accounts for the last 10% and is initiated again by nervous stimuli associated with distention of the small intestine.

The Pancreas Exocrine function (98%) Endocrine function –
Acinar cells make, store, and secrete pancreatic enzymes Endocrine function –  cells (delta cells) release somatostatin (inhibitory to gastrin and insulin and glucagon) β-cells –release insulin α-cells-Release glucagon Although the stomach has an enzyme to start protein digestion, and the small intestine has multiple enzymes within its brush border for carbohydrate digestion, protein digestion, and lipid digestion, the organ that releases the most substantial digestive enzymes is the pancreas. 98% of its physiology is dedicated to an exocrine function in the synthesis and release of digestive enzymes by the Pancreatic Acini (that’s the cell type in the pancreas that makes these enzymes—and I will cover all of these in the next few slides. The remainder of the pancreas is dedicated to an endocrine function with the production and secretion of hormones into the blood stream. These hormones include insulin (which stimulates insulin dependent cells of the body to express glucose transporters and then glucose can be imported within the cell’s cytoplasm. As glucose leaves the blood plasma and enters insulin dependent cells, the blood plasma glucose levels declines. Insulin is synthesized and released by the Beta-cells of the Islets of Langerhans. In contrast, when blood glucose levels decline too much, the alpha-cells of the islets of Langerhans release glucagon which stimulates the liver to cleave glycogen (a polymerized form of glucose) into single monomers of glucose. There are other endocrine cells within the Islets of Langerhans (delta cells for example) that release hormones like somatostatin which is a hormone that shuts down all hormonal functions of the kidney and stops gastrin.

The Pancreas as an Endocrine Gland
Insulin Beta cells Promotes glucose uptake Prevents fat and glycogen breakdown and inhibits gluconeogenesis Increases protein synthesis Promotes fat storage Epi/Norepi inhibit insulin! Help maintain glucose levels during times of stress and increase lipase activity in order to conserve glucose levels Insulin is the only hormone known to have a direct effect in lowering blood glucose levels. It is synthesized and released into the blood stream by the beta cells of the islets of Langerhans. Most tissues of the body, like skeletal muscle and adipose tissue are insulin dependent in order to move glucose into the body tissues. The main exception is the brain. Because most cell membranes are impermeable to glucose, they require a special carrier, called a glucose transporter, to move glucose from the blood into the cell. Within seconds of binding insulin, the membranes of about 80% of body tissues increase their uptake of glucose by means of special glucose transporters. This is particularly true of skeletal muscle and adipose tissue. In addition to promoting glucose uptake, insulin prevents fat and glycogen breakdown and inhibits gluconeogenesis, and increases protein synthesis. Gluconeogenesis means the synthesis of new glucose molecules by converting amino acids or glycerol into new glucose molecules. Insulin also promotes fat storage by increasing the rate of movement of glucose into fat cells which is then converted into fat. Insulin also inhibits protein breakdown and increases protein synthesis. As a side note: catecholamines (like epi/norepi) help to maintain blood glucose levels during periods of stress. Epinephrine inhibits insulin release and promotes glycogenolysis by stimulating the conversion of muscle and liver glycogen to glucose. Muscle glycogen cannot be released into the blood; nevertheless, the mobilization of these stores for muscle use conserves blood glucose for use by other tissues such as the brain and the nervous system. During periods of exercise and other types of stress or fear, epinephrine inhibits insulin release from the beta cells and thereby decreases the movement of glucose into muscle cells. The catecholamines also increase lipase activity and thereby increase mobilization of fatty acids, a process that conserves glucose. The blood glucose-elevating effect of epinephrine is an important homeostatic mechanism during periods of hypoglycemia in insulin-treated patients with diabetes. I will talk about Diabetes Mellitus type 1 and type II in the next two slides. Picture from:

The Pancreas as an Endocrine Gland
Glucagon Increases blood glucose levels Maintains blood glucose between meals and during periods of fasting by breaking down glycogen (stored in liver) into glucose. Initiates glycogenolysis in liver (within minutes). Stimulates gluconeogenesis. This process involves breaking down amino acids (proteins) into glucose. Stimulates amino acid transport to liver to stimulate gluconeogenesis Nervous tissue (brain) does not need insulin; but is heavily dependent on glucose levels! Glucagon is a polypeptide molecule produced by the alpha cells of the islets of Langerhans and maintains blood glucose levels between meals and during periods of fasting. The most dramatic effect of glucagon is its ability to initiate glycogenolysis or the breakdown of liver glycogen as a means of raising blood glucose, usually within a matter of minutes. Glycogenolysis means that the liver hydrolyzes glycogen to release free glucose molecules into the blood stream. Although many tissues and organ systems are able to use other forms of fuel, such as fatty acids and ketones, the brain and nervous system rely almost exclusively on glucose as a fuel source. Because the brain can neither synthesize nor store more than a few minutes’ supply of glucose, normal cerebral function requires a continuous supply from the circulation. Severe and prolonged hypoglycemia can cause brain death and even moderate hypoglycemia can result in brain dysfunction. Glucagon also increases the transport of amino acids into the liver and stimulates their conversion into glucose. Image from:

Liver and Gallbladder The liver produces bile that is either stored by the gallbladder or secreted into the small intestine. Bile emulsifies fats and fat-soluble vitamins. It also helps keep the small intestine free from parasites. The liver does not make the digestive enzymes for carbohydrates, amino acids and proteins (the pancreas and small intestine do that), but the liver does metabolize proteins, carbohydrates and cholesterol. It also is responsible for the detoxification of toxins, drugs and hormones.

Large Intestine The large intestine absorbs water, electrolytes and some of the final products of digestion. Food products that cannot go through the villi, such as cellulose (dietary fiber), are mixed with other waste products from the body and become hard and concentrated feces.

Physiology of the large intestine
Reabsorption of water and electrolytes Coliform bacteria make: Vitamins – K, biotin, and B5 Organic wastes are left in the lumen By the time our chyme passes through the ileocecal valve, the volume has diminished from 9L down to 1200ml. In the large intestine, the proximal half of the colon is important for absorption of electrolytes and water. The mucosa of the large intestine has a high capability for active absorption of sodium, and the electrical potential created by absorption of sodium causes chloride absorption as well. The tight junctions of the large intestine are tighter than those of the small intestine, which decreases back diffusion of ions through these junctions. This allows the large intestinal mucosa to absorb sodium ions against a higher concentration and prevents back leak of ions into the lumen. Thus the absorption of sodium and chloride ions creates an osmotic gradient across the large intestinal mucosa, which in turn causes absorption of water. The large intestine can reabsorb about 5-7 liters of fluid and electrolytes a day. If the total quantity of chyme entering the large intestine is greater than this, then the excess appears in the feces as diarrhea. What is in feces? It is about 30% dead bacteria, percent fat, percent inorganic matter, 2-3 percent protein, and 30% undigested roughage of food and bile and sloughed epithelial cells. The brown color is from the stercobilin and urobilin, which are derivatives of bilirubin. This concludes our discussion on the physiology of the digestive tract.

Phases of gastric secretion
Cephalic phase Gastric phase Intestinal phase

Cephalic phase This phase occurs before food enters the stomach and involves preparation of the body for eating and digestion. Sight and thought stimulate the cerebral cortex. Taste and smell stimulus is sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve and release of acetylcholine. Gastric secretion at this phase rises to 40% of maximum rate. Acidity in the stomach is not buffered by food at this point and thus acts to inhibit parietal (secretes acid) and G cell (secretes gastrin) activity via D cell secretion of somatostatin.

G cell secretion of gastrin D cell secretion of somatostatin

G cells and Gastrin G cells are found deep within the gastric glands of the stomach. When food arrives in the stomach, the parasympathetic nervous system is activated. This causes the vagus nerve to release a neurotransmitter called Gastrin-releasing peptide onto the G cells in the stomach. Gastrin-releasing peptide, as well as the presence of amino acids in the stomach, stimulates the release of gastrin from the G cells. Gastrin tells parietal cells to increase HCl secretion, and it also stimulates other special cells to release histamine. Gastrin also tells the chief cells to produce pepsinogen. Gastrin is inhibited by low pH (acid) in the stomach. When enough acid is present, it turns off.

Gastrin Stomach distension Vagus nerve stimulation
Gastrin is released in response to Stomach distension Vagus nerve stimulation The presence of proteins or amino acids Gastrin release is inhibited by The presence of enough HCl in the stomach (negative feedback) Somatostatin also inhibits the release of gastrin

D cells D cells can be found in the stomach, intestine and the Islets of Langerhans in the pancreas. When gastrin is present, D cells increase somatostatin output. When D cells are stimulated by Ach, they decrease somatostatin output.

Somatostatin Somatostatin is also known as growth hormone-inhibiting hormone. It suppresses the release of gastrointestinal hormones Gastrin Cholecystokinin (CCK) Secretin GIP It suppresses the release of pancreatic hormones. It slows down the digestive process. It inhibits insulin release. It inhibits the release of glucagon.

Gastric phase This phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH. This activates the release of acetylcholine which stimulates the release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin, which in turn stimulates parietal cells to secrete gastric acid. Acid release is also triggered by acetylcholine and histamine.

Intestinal phase This phase has 2 opposing actions: the excitatory and the inhibitory. Partially digested food fills the duodenum. This triggers gastrin to be released. It also triggers the enterogastric reflex, which inhibits the Vagus nerve. This activates the sympathetic nervouse system, which causes the pyloric sphincter to tighten to prevent more food from entering the duodenum.

Digestive Enzymes Salivary glands -amylase lingual lipase Stomach
pepsin Intestinal Mucosa sucrase maltase lactase Pancreas amylase trypsin chymotrypsin carboxypeptidase lipase cholesterolesterase

The Activities of Major Digestive Tract Hormones
Let’s do the hormones again, this time with the big picture involved. Once food enters the stomach, the G-cells within the gastric glands of the antrum release Gastrin. Gastrin stimulates the parietal cells to release more acid and also promotes more motility of the stomach. This means the contents of the stomach are churned and mixed to form chyme. Next, the chyme travels through the pylorus and enters the duodenum. The presence of chyme now triggers the release of the other 3 major digestive tract hormones: cholecystokinin, secretin, and gastric inhibitory peptide. Secretin stimulates the pancreas to release bicarbonate rich buffer. Gastric inhibitory peptide primarily slows down stomach motility and slows the rate at which the stomach empties chyme into the duodenum. Cholecystokinin stimulates the liver, gallbladder and pancreas. The liver and gallbladder are stimulated to secrete and release, respectively, bile into the duodenum through the hepatopancreatic ampulla. CCK stimulates the pancreas to release its digestive enzymes that include enzymes for carbohydrate digestion, lipase, nucleases, and peptidases. All four hormones stimulate the pancreas to release insulin in a sort of “anticipatory” effect for food. The insulin then stimulates insulin dependent cells of the body to start inserting glucose transport proteins into the cell membranes. These glucose transporters bind to glucose and facilitate its movement from the plasma to the cytoplasm. OF the four hormones, Gastric inhibitory peptide seems to have the strongest influence on insulin release. Figure 24.22

Organ Region of the Organ Substances Function
Pancreas Acinar cells Amylase (enzyme) Breaks down starch and carbohydrates into glucose Lipase (enzyme) Breaks down fat into fatty acids Protease enzymes (trypsin, chymotrypsin, carboxypeptidase) Breaks down proteins into amino acids and also kills intestinal parasites and bacteria Bicarbonate (not an enzyme) Raises pH in duodenum Islet of Langerhans; Alpha cells glucagon (hormone) Causes glycogenolysis, the process which breaks down glycogen into glucose to raise blood glucose. Also causes gluconeogenesis to make new glucose molecules Islet of Langerhans; Beta cells insulin (hormone) Removes glucose in bloodstream and brings it into cells. Lowers blood glucose levels. Islet of Langerhans; Delta cells Somatostatin (hormone) Inhibits gastrin, insulin, and glucagon (inhibits digestive system) Liver Bile (a detergent) Salivary glands Stomach Mucous (not an enzyme) Protect the stomach lining Prostaglandins (not an enzyme) Parietal cells HCl (not an enzyme) Allows Pepsinogen to be converted to pepsin, and it also kills bacteria Intrinsic factor (not an enzyme) Allows Vit B12 to be absorbed, which is needed to make RBCs. Without it, you get megaloblastic (pernicous) anemia. Chief cells Pepsinogen --> pepsin (enzyme) Breaks proteins into amino acids G cells Gastrin (hormone) Tells parietal cells to secrete HCl Duodenum Secretin (hormone) Tells pancreas to secrete bicarbonate CCK (hormone) Tells pancrease to secrete proteases, and tells gallbladder to release stored bile (stimulates fat and protein digestion) K cells GIP (hormone) Tells pancreas to release insulin and also causes fat to be broken down into fatty acids Motilin (hormone) Initiates perstalsis and tells Chief cells to secrete pepsinogen Maltase, Lactase, Sucrase (enzymes) Break down complex carbohydrates into glucose

The Ovaries Small, almond-shaped organs, each 1 ½” x 1”
Within the peritoneal cavity on the posterior body wall Covered by a superficial epithelium called the VISCERAL PERITONEUM. Held in place by mesentery called MESOVARIUM Also held in place by ligaments BROAD LIGAMENT: where the mesentery attaches to the uterine (fallopian) tube; this is an extension of the mesovarium. SUSPENSORY LIGAMENT: holds the ovary superiorly OVARIAN LIGAMENT: connects ovary to the uterus Ovarian arteries – arterial supply through the mesentery to the ovary

The Female Reproductive System
Figure 24.11a

Female Internal Reproductive Organs
Figure 24.10

Ovary Medulla Cortex Tunica albuginia Primary follicle
Secondary follicle Graafian follicle

Primary Follicle The oocyte is surrounded by a group of cells called FOLLICULAR CELLS. The whole structure is called the PRIMARY FOLLICLE. At puberty there is a change in hormones which causes development of some of these oocytes. Primary Follicle Oocyte Follicular cells

The Ovarian Cycle Ovulation – occurs about halfway through each ovarian cycle Oocyte exits from one ovary (it is now called an ovum) Enters the peritoneal cavity Is swept into the uterine tube Luteal Phase – occurs after ovulation Remaining follicle becomes a corpus luteum Secretes progesterone Acts to prepare for implantation of an embryo

The Ovarian Cycle Secondary follicles with oocyte
Primary follicles with oocyte Graafian follicle with oocyte ovum corpus luteum Figure 24.13

The average ovarian cycle is 28 days.
This is the first day of menstruation. The primary follicle begins to develop. The female sex cycle begins on the first day of menstruation.

OVARIAN CYCLE Day 1-7 The oocyte develops and the follicle cells grow and divide. The adenohypophysis secretes FSH (follicle stimulating hormone). This causes eggs to be stimulated in both ovaries.

Day Day 7

SECONDARY FOLLICLE It has now become a SECONDARY FOLLICLE, which starts to produce the hormone ESTROGEN. Estrogen causes a build up the lining of the uterus and also inhibits the development of the follicles.

The Ovarian Cycle Secondary follicles with oocyte
Primary follicles with oocyte Graafian follicle with oocyte ovum corpus luteum Figure 24.13

Day 14: GRAAFIAN FOLLICLE
The follicle is fully mature = GRAAFIAN FOLLICLE. The oocyte is now fully mature = ovum The ovum is surrounded by a ring called the CORONA RADIATA. It is then surrounded by a space = ANTRUM, which contains a clear fluid. The antrum is surrounded by the follicular cells.

OVULATION The mature follicle is still producing estrogen. It has become so big that it forms a blister on the outside of the ovary. The adenohypophysis secretes another hormone called LH (leuteinizing hormone). LH causes fluid to rapidly flow into the antrum, which then expands and pops, which also breaks through the tunica albuginia. The egg and corona radiata are released into the peritoneum. This process is called OVULATION. Can be some pain.

Ovulation

OVULATION The follicle cells that are leftover remain in the ovary and are called the CORPUS LUTEUM (“yellow body”). After a pregnancy the corpus luteum disintegrates into dead tissue; a white scar called the CORPUS ALBICANS (“white body”). In autopsy, you can see how many of these scars are present to determine the number of pregnancies she had.

The Ovarian Cycle CORPUS ALBICANS corpus luteum Figure 24.13

Day 14-21 The egg takes a week to make its way down to the entrance of the uterus. The follicular cells continue to grow and now they make progesterone, which builds the uterus lining so it’s ready for the egg by the time it gets there.

Ovarian Cycle Day 23 If no fertilization, the egg starts to break down. Day 27 There is no more estrogen. Day 28 Menstruation starts as the uterine lining breaks down  Day 1

FERTILITY PILLS Women who have trouble conceiving take fertility pills = FSH, which causes 100 follicles to develop, 4-5 of which may mature  multiple births.

BIRTH CONTROL PILLS Birth Control Pills are made of estrogen, so they inhibit the development of the follicles, but the uterine lining still grows. They are taken for 3 weeks, then one week is taken off to allow for menstruation. Some of the new estrogen pills can cause a period only every 3 months instead, but there are side effects.

Estrogen The estrogen allows for deposition of subcutaneous fat, which is what gives women their curves. In pregnancy, the breasts get larger, the mammary glands get bigger.

Fertilization If the egg is fertilized, the corpus luteum grows until the pregnancy is over and then disintegrates into the CORPUS ALBICANS, which is a scar that can be seen on autopsy; reveals the number of pregnancies she had.

UTERINE (FALLOPIAN) TUBES
The ovary is in the peritoneal cavity, surrounded by the peritoneum, with an egg releasing. The uterine tube has FIMBRIAE (“fingers”) that surround the ovary. When the egg is released, it goes into the peritoneal cavity, but the CILIA that line the uterine tube create a current that drags the egg in.

Uterine Tube

UTERINE(FALLOPIAN ) TUBES
The uterine (fallopian) tubes are held up by the broad ligament and the suspensory ligament. The uterine tubes are about 10cm long (3”), but only 7/10cm in diameter, and the actual lumen where the tube enters the uterus is tiny.

The Uterine Tubes Figure 24.11a

The Uterine Tubes The uterine tube is made of the INFUNDIBULUM (funnel), the AMPULLA (most of the tube), and the ISTHMUS (the part of the tube closest to the uterus). The ampulla is where fertilization usually occurs. If the egg implants outside of the uterus or on the external surface of the wall of the uterus, it is called an ECTOPIC PREGNANCY. The most common location for an ectopic pregnancy is the uterine tubes.

ECTOPIC PREGNANCY The egg is normally fertilized in the uterine tube, goes down into the uterus and implants there. If it implants anywhere else, it is called an ECTOPIC PREGNANCY. If it implants in the uterine tube = TUBAL PREGNANCY, a type of ectopic pregnancy. The uterine tube is the most common location for an ectopic pregnancy. Ectopic pregnancies are fatal to the mother and embryo, but nowadays there are few deaths of the mother because it is very painful, so she will go to the ER and they will do surgery.

PELVIC INFLAMMATORY DISEASE
Sperm swim out of the opening of the uterine tube and into the peritoneal cavity. That means any STD can also enter there, causing PELVIC INFLAMMATORY DISEASE (PID), which is when it spreads to the ovaries. It could then continue to all organs in the pelvis EXCEPT those organs which are retroperitoneal (Kidney, ureter, and urethra). It includes SALPINGITIS (inflammation of the uterine tube).

PID The most common cause of PID and infertility in women is STD, usually Chlamydia or gonorrhea. The inflammation and scarring closes off the uterine tube; although PID does not inhibit ovulation, it can lead to sterility.

UTERUS Endometrium

UTERUS It is held in place by by the ROUND LIGAMENT and mesentery = the BROAD LIGAMENT. When a woman stands upright, the uterus sits on top of the urinary bladder

The Female Reproductive System
Figure 24.11a

Layers of the Uterus ENDOMETRIUM (two layers) STRATUM FUNCTIONALE
STRATUM BASALE: the deeper layer, can divide and grow to replace itself.

UTERUS The stratum functionale develops with the hormone cycle, which causes it to grow, along with its glands and blood vessels. When the hormones stop, the stratum functionale breaks down, leaving only the stratum basale.

UTERUS Deep to the endometrium is the MYOMETRIUM, made of smooth muscles which contract during birth. The PERIMETRIUM (Or Epimetrium) is the name of the visceral perineum.

ENDOMETRIOSIS Pieces of the endometrium are supposed to fall down the vagina, but sometimes its cells go up the uterine tube and enter the peritoneal cavity. They can lodge anywhere; on top of the fundus, even on the lung pleura. One lady got a collapsed lung every month!

FIBROIDS These are benign tumors like scar tissue in the myometrium. They can get large and be painful, especially during contraction of menses and pregnancy. Fibroids are the most common reason for hysterectomy (surgical removal of the uterus).

EXTERNAL GENITALIA = VULVA
Parts of the vulva MONS PUBIS is a pad of adipose tissue above the pubic symphysis, covered with pubic hair. LABIA MAJORA is an extension on either side of the vestibule, also with pubic hair. It is the female equivalent of the scrotum. LABIA MINORA is medial to the labia majora. They are thin folds of tissue and erectile tissue. CLITORIS (equivalent of the penis), which also has erectile tissue. The clitoris is covered by a PREPUCE and has a CORPORA CAVERNOSA.

The External Genitalia and Female Perineum
Figure 24.20

EPISIOTOMY A purpose of an episiotomy during childbirth is to minimize tearing of the central tendon and muscles of the pelvic floor.

Reproductive System Cancers in Females
Ovarian cancer – arises from cells in the germinal epithelium Endometrial cancer – arises from the endometrium of the uterus Cervical cancer – slow-growing, arises from epithelium at the tip of the cervix

Reproductive System Cancers in Females
Breast cancer – Second most common cause of cancer deaths in women 97% occurs in women over 50 Usually arises from cells in the milk ducts When the skin is dimpled from breast cancer, the suspensory ligaments of the breast are causing the dimpling. Treatment Surgical removal of the mass (lumpectomy) Radiation therapy Administration of selected hormones Chemotherapy

Embryology Embryology – study of the origin and development of single individual This is an amazing process that one cell can grow into an entire organism is 9 months! Remember, typical (diploid) cells of the body have 46 chromosomes; and each gamete has 23 chromosomes. -At the moment of conception, you spent about half an hour as a single cell.

Fertilization occurs in the ampulla portion of the uterine tube.
The most common site of ectopic pregnancy is the uterine tube Figure 3.3

hCG Hormone The trophoblast cells secrete a hormone = hCG (human chorionic gonadotrophin). This hormone maintains the growth of the uterine lining. If no hCG is present, there will be menses. hCG is the hormone which is measured in a pregnancy test. It will be in sufficient quantities to be measured within about one week after a missed period.

Implantation CHORIONIC VILLI are projections from the fetus that burrow into the uterus. The capillaries within a chorionic villus of the placenta contain blood from the fetus only, not the mother. Therefore, this tissue can be used for genetic testing for birth defects. Figure 3.4

FETAL DEVELOPMENT The heart starts to pump during the fourth week.
Male and female fetuses can first be distinguished by their genitals at 3 months.

Birth Defects FETAL ALCOHOL SYNDROME from the mother drinking alcohol is the most common cause of mental retardation in the United States. The most common birth defects world-wide involve the heart and circulation.

Fetal Alcohol Syndrome

Birth Defects A TERATOGEN (“monster maker”) is any chemical, physical, or biological agent that induces birth defects. THALIDOMIDE was a medicine used for morning sickness in the late 1950’s and early 1960’s until it was found to cause the babies to be born without arms and legs. About 20,000 babies in 46 countries were affected.

Teratogen Affect

EMBRYONIC DEVELOPMENT OF THE SCROTUM
7 Months in utero The testis (singular) is retroperitoneal, located up high, above the pubic symphysis. The vas deferens comes off it. A fibrous band = GUBERNACULUM goes from the pubic symphysis and inserts onto the skin under the penis.

7 Months

8 Months The gubernaculum shrinks, and testes are pulled down. The peritoneum forms a pouch =VAGINAL PROCESS. The abdominal muscles come down and goes around the testes.

8 months

Birth The vaginal process is pinched off, forming the TUNICA VAGINALIS. The vas deferens goes into the abdominal cavity. The DARTOS MUSCLE (cutaneous) lines the scrotum, leading in to the CREMASTER MUSCLE. The function of the cremaster muscle is to help keep a gonad cool or warm.

Decent of the Gonads Figure 24.29a-c

Spermatic Cord Vas deferens (ductus deferens) Cremaster muscle
Spermatic (testicular) artery and vein Pampiniform plexus (Nerves and lymphatic vessels). The Dartos and cremaster muscles both elevate the testes in the cold so they can stay warm, and they relax in the heat to allow the testes to descend to stay cool. Tight underwear can cause a low sperm count

ERECTION IN MALES The erectile tissue is lined by tissue which extends into itself, creating vascular spaces which can fill with blood, causing the penis to become more rigid and expand. The erection is due to vasodilation, with blood moving into erectile tissue.

The Male Reproductive System
The testes: this is the primary sex organ in the male, not the penis. The scrotum – skin and superficial fascia surrounding the testes Positioning provides an environment 3˚ cooler than body temperature Dartos muscle – layer of smooth muscle Cremaster muscle – bands of skeletal muscle surrounding the testes Elevates the testes

Testes In order for sperm to be produced, the temperature has to be a few degrees lower than normal (3˚ cooler). To insure a lower temperature, the testes are located outside of the body, in the scrotum (outside of the pelvis). The temperature is maintained by muscles that elevate and depress the testes.

Problems at Birth 1. CONGENITAL INGUINAL HERNIA
The vaginal process doesn’t close off completely, and a piece of intestine gets caught there INGUINAL HERNIA If you do heavy lifting, it increases the abdominal pressure, and a piece of intestine gets pushed into the opening called the inguinal canal. Requires surgery. 2. UNDESCENDED TESTES Sperm will still be able to exit from the body, male sex hormones will still circulate in the body, and the testes will still have adequate blood supply. However, viable sperm will not be produced. Needs a surgery to yank them down.

Structure of the Testes
Are enclosed in a serous sac – the tunica vaginalis Tunica albuginea – fibrous capsule of the testes Divides each testis into lobules Lobules contain 1-4 coiled seminiferous tubules

The Testes Figure 24.3a

The Seminiferous Tubules
They are 70 cm (2 feet) long. Function of seminiferous tubules is to make sperm. Spermatogenic cells – sperm-forming cells Columnar sustentacular cells – support cells

Interstitial Cells Between the seminiferous tubules are groups of cells = INTERSTITIAL CELLS, which produce testosterone.

Epididymis The seminiferous tubules come together to form the EPIDIDYMIS, the tube of which is 5 meters (the width of this room!). The function of the epididymis is to allow sperm to mature and to store them. It takes 20 days for the sperm to go from production to storage. If sperm is not ejaculated, it will just die and be phagocytyzed. The epididymis has smooth muscles for peristalsis during ejaculation to move the sperm along.

The Epididymis Tube leading out of the epididymis Figure 24.3a

Spermatic Cord The SPERMATIC CORD leaves the epididymus and contains the spermatic artery, vein, nerves, and the DUCTUS (VAS) DEFERENS which is the tube that carries the sperm out of the epididymis. The Vas deferens is long, 45cm (2 feet). It goes through the inguinal canal, loops around urinary bladder and down the other side. It’s easy to see on a cat.

The Ductus (Vas) Deferens
Figure 24.1

The Spermatic Cord Figure 24.2

Most common cause of infertility
In spermatic cord is a network of vessels. The veins there can become varicose = VERICOCELE. As they expand, there is less blood flow, temperature drops in testes leading to infertility. Second most common cause of infertility is STD (inflammation blocks vas deferens).

Seminal Vesicles Posterior to the urinary bladder = SEMINAL VESICLES
The EJACULATORY DUCT meets up with the PROSTATIC URETHRA in the prostate.

Seminal Vesicle Figure 24.1

Seminal Fluid The functions of the seminal vesicles (60%) and the prostrate (40%) are to produce most of the seminal fluid (seminal fluid plus sperm = semen).

Functions of the Semen Medium for sperm to swim in
Nutrients for sperm (fructose) Neutralizes acidity in vagina to allow sperm to survive

Prostate The urethra goes through the middle of the prostate, and the prostate continues to grow throughout life. PROSTATIC HYPERTROPHY Can constrict the urethra, causing retention of urine because it is hard to urinate. Needs surgery to open.

Final Journey of the Sperm
The vas deferens picks up fluid from the prostate, and the semen enters the urethra. It picks up more secretions from the bulbourethral glands.

BULBOURETHRAL GLANDS At the base of the urethra
Secretes mucous during erection Function is to lubricate the urethra for sperm to swim in and neutralize pH from urine there. It allows the semen to flow and survive. Only a small amount of fluid is produced.

Review The testes are the primary sex organ in the male because it makes the hormone that creates secondary male sex characteristics. A male secondary sex characteristic is a deep voice, facial hair, prominent thyroid cartilage. Sperm is made in the testes, goes into the vas deferens, loops over the urinary bladder, and goes into the seminal vesicle and prostate gland.

Bulbourethral Gland Figure 24.1

Cross-Section of Penis
In cross-section, within the penis there are three tubes (2 posterior) called CYLINDERS OF ERECTILE TISSUE. The posterior two are the CORPUS CAVERNOSUM (Corpora cavernosa, plural). The anterior one is the CORPUS SPONGIOSUM, within which is the urethra.

Cross-Section of Penis

The Penis Figure 24.8a, b

Penile Erection The erectile tissue in the corpora cavernosa is lined by dense fibrous connective tissue which extends into itself, creating vascular spaces which can fill with blood, causing the penis to become more rigid and expanding. The erection is due to vasodilation, with blood moving into erectile bodies (tissue). The corpus spongiosum doesn’t get as rigid or it would squeeze urethra shut.

Viagra Medicine which allows vasodilation, but if you have heart disease, it can give you a heart attack. An erection squeezes the veins shut so the blood can’t leak out. If Viagra (or anything else) causes an erection for longer than four hours (called priapism), the erection decreases the blood flow, and the tissue is killed.

Other Problems with the Penis
Hypospadia is the most common congenital abnormality of the urethra, and is in males only. The skin around the urethra does not close all the way, and the urethra is open to the outside of the body. It requires surgical closure within one year of birth.

Hypospadias

Reproductive System Cancers in Males
Testicular cancer Affects 1 of 50,000 males Cured in 95% of cases Prostate cancer Slow-growing Risk factors Fatty diet Genetic predisposition

Digestive System.

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