Digestive System http://www.youtube.com/watch?v=0gY-zXsUYgs

Humans as Heterotrophs Hetero=another Trophe= nutrition As heterotrophs we cannot convert carbon therefore we ingest carbon in our food. All of our cells require nutrition for; Growth Repair Maintenance Humans as Heterotrophs Hetero=another Trophe= nutrition Inorganic Carbon= CO2, Carbon Fixation= Autotrophs

Functions of the Digestive System Break down of food into nutrients. Nutrients absorbed in the body. Transported throughout the circulatory system. Nutrients in the cell can be used as a source of energy OR Used for the synthesis of chemical compounds

Stages of the Digestive System Absorption Egestion Ingestion Digestion

1. Ingestion Ingestion occurs when food enters the mouth. It is mechanically broken down by teeth 1. Ingestion

Chewing stimulates the release of saliva from the salivary organs. Saliva contains a mixtures of water, mucus and enzymes. 1. Ingestion: Cont. Starch to sugars

Enzyme that breaks starch down into simple sugars. 1. Ingestion: Amylase

Food that has been chewed and mixed with saliva becomes a bolus. 1. Ingestion: Bolus The epiglottis, a flap of skin directs food down the esophagus. Pharynx: Either food or air can enter here. Before the Larynx (air) and the Esophagus.

1. Ingestion: Peristalsis When the bolus has entered the esophagus muscle contractions (peristalsis) move it towards the stomach. 1. Ingestion: Peristalsis

2. Digestion: Stomach Digestion occurs initially in the stomach. The stomach is J-shaped, it stores food, and has a capacity of 1.5 L 2. Digestion: Stomach

2. Digestion: Sphincters Food enters and exits the stomach through sphincters. Sphincters are muscles surrounding a tube-like structure The bolus enters the stomach when the cardiac sphincter relaxes. 2. Digestion: Sphincters

2. Digestion: Gastric Juice The stomach contains gastric juice secreted by the stomach lining. Gastric juice contains a mixture of: HCL (hydrochloric acid) Enzymes Mucus 2. Digestion: Gastric Juice

2. Digestion: Gastric Juice HCL Breaks down fibres & Bacteria Mucus Protect stomach lining from HCL If stomach lining is destroyed ulcers form. 2. Digestion: Gastric Juice Gastric juices are eating through the lining, digesting itself since there is no protection from the mucus.

Heliobacter pylori H. Pylori attaches itself to the stomach lining using flagella penetrating the mucus lining. It will harm the stomach and the duodenum causing ulcers and gastritis. Present in about 50% of the world** Verify. Focus on stomach ulcers. The Nobel Prize in Physiology or Medicine 2005 Barry J. Marshall and J. Robin Warren "for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease"

2. Digestion The stomach absorbs: Water Alcohol Some medications (Aspirin) 2. Digestion

Chyme travels out of the stomach by the pyloric sphincter into the small intestine. Chyme is a mixture of: Water Digested food Gastric Juices 2. Digestion: Chyme

2. Digestion: Small Intestine After the pyloric sphincter chime enters the duodenum Duodenum is first 25cm of the small intestine. 7m in length, 2.5m in diameter. 2. Digestion: Small Intestine

2. Digestion: Duodenum Majority of digestion occurs here. Secretions from pancreas and duodenum enter via a duct. 2. Digestion: Duodenum

2.Digestion: Liver Has four functions in digestion: Synthesis Breakdown Detoxification Storage 2.Digestion: Liver

Synthesis Produces bile which breaks down fats. Bile is stored in the gallbladder Synthesis

Bile is an emulsifier (a compound used to mix immiscible substances) This allows for the breakdown of fats and for travel through the digestive system. 1. Synthesis: Bile Emulsification-Mayo

1. Synthesis: Gallstones Gallstones occur when too much bile or concentrated bile is produced in the gallbladder. The bile will crystalize into gallstones blocking the gallbladder. 1. Synthesis: Gallstones

Process of removing Nitrogen group from Amino Acids to create urea. 2. Breakdown

When there is a blockage of the gallbladder Jaundice can occur (yellowing of the skin). 2. Breakdown: Jaundice

3. Detoxification Removes toxins from the body including Alcohol Chemicals 3. Detoxification

4. Storage Vitamins and carbohydrates are stored in the liver.

Increases the pH of chyme from 2 Increases the pH of chyme from 2.5 to 9 due to the production of sodium bicarbonate. Secretes enzymes for digestion Lipase (fats) Trypsin (proteins) Pancreas

Small Intestine Secretes Maltase (maltose - > glucose) Peptidase (protein breakdown) Duodenum (beginning), Jejunum (middle), Ileum (end).

Food & Enzymes Carbohydrates -> Glucose Proteins -> Amino Acids (amylase & maltase) Proteins -> Amino Acids (pepsin & peptidase) Fats (triglycerides) -> Fatty Acids & Glycerol (bile & lipase) Food & Enzymes Amylase: Enzyme in the saliva Starch to sugars.

The jejunum and ileum contain villi (finger like projections) which increase the surface area. The villi help with absorption of Glucose Amino Acids Fatty Acids Glycerol 3. Absorption

Once nutrient are absorbed through the villi they enter the blood stream and are dispersed throughout the body 3. Absorption

Digestive System

3. Absorption: Large Intestine Water absorption Bacteria living in colon releasing Vitamin K & B, also absorbed.

Cellulose aids in the ejection of material from the bowels. Lack of cellulose in the diet can lead to colon cancer. 4. Egestion Celery dietary roughage. Sphincter

Digestive System The entire process takes 24-36 hours.

Homeostasis The ability of the body to regulate according to the fluctuating internal and external environment Homeostasis:

Digestion & Homeostasis Nervous and hormonal system aid digestion before we eat. Seeing, smelling and tasting food stimulates production of gastric secretions. Digestion & Homeostasis

Digestion & Homeostasis Cont. Swallowing stimulate the production of gastric juices. Gastrin (hormone) stimulates the release of gastric juice before food arrives. Digestion & Homeostasis Cont.

Digestion Speed of Digestion: Large meals with digest quickly due to strong stomach contractions and faster emptying. Fatty meals slow down digestion due to a hormone response from the small intestine. Digestion

Homeostasis Receptors in the body sense: Blood Sugar levels Body T Oxygen level Disruption in homeostasis -> Signal to brain for correction Homeostasis

Homeostasis: Blood Sugar Concentration crucial to well being Too low body shuts down (coma) Eating increases blood sugar (glucose) Homeostasis: Blood Sugar

Homeostasis: Blood Sugar Body releases insulin from pancreas to bring glucose inside cells. Extra glucose taken by liver cells and convert to glycogen and stored. Homeostasis: Blood Sugar Insulin: Activates cell surface.

Homeostasis: Blood Sugar normal glucose high glucose food low glucose insulin release (pancreas) cells take up excess glucose, liver makes glycogen glucagon release glycogen release as glucose (liver) Decrease in blood sugar pancreas will be activate to release glucagon Glucagon (hormone) will convert glycogen (in liver), back to glucose, which will be released into the blood. Homeostasis: Blood Sugar