UNIT 4 ANIMALS STRUCTURE & FUNCTION

Four stages of food processing 1.Ingestion: taking in/eating of food 1.Digestion: breaking down food (mechanically/chemically) into nutrients 2.Absorption: taking in of nutrients by cells = transport of products into circulatory system and to the rest of the body 3.Elimination: removal of undigested solid wastes

10.2 The Path of Digestion

Pathway of Digestion Mouth  Esophagus  Esophagial sphyncter  Stomach  Phyloric sphincter  Small intestine  Large intestine  Rectum  Anus

Digestion - Mouth The smell or sight of food can trigger salivary glands to produce saliva Saliva contains Amylase (Carbohydrase) Saliva is responsible for: 1) stimulating taste buds 2) lubricating food 3) chemical digestion (amalyse) The mouth is also responsible for the breakdown of food. This creates more surface area to facilitate chemical digestion

Esophagus What is this called? Food going down the esophagus has a new name, bolus. The cardiac sphincter opens to allow the bolus of food to enter the stomach. Contraction and relaxation of the smooth muscle down the esophagus moves the bolus down to the stomach. This movement is called peristalsis.

Esophagus – Peristalsis Esophagus Peristalsis Esophagus: muscular tube through which food passes from mouth to stomach Peristalsis: wave-like muscular contraction in esophagus

Stomach The stomach functions under low acidity Food is broken down through: 1.The HCl 2.Churning of the stomach 3.Pepsin (protease that functions under low pH) Food leaves the stomach through the pyloric sphincter

Protection of the Stomach Lining The stomach is very acidic so why does it not eat itself? Food stimulates the production of gastric juice The stomach produces mucus (basic) which prevents the acidity of the stomach from harming the lining. Pepsin is activated by gastric juices.

Small Intestine Composed of 3 parts: Duodenum Jejunum Ileum Consists of proteases, lipases, and carbohydrases Majority of nutrients are absorbed into the circulatory system Chyme leaves the S. I. through the ileocecal valve

Villi and Microvilli of the Small Intestine

The role of accessory organs Pancreas Secretes ~1 L of pancreatic fluid/day containing carbohydrases/lipases/proteases into the duodenum Secretes bicarbonate into duodenum to counter balance acidity from stomach Allows enzymes secreted by pancreas to function because they need a more neutral pH

The role of accessory organs Liver Secretes bile to emulsify fats Amino acids are processed Gallbladder Stores bile Release into duodenum when needed (after mealtime!)

Enzymes – pg 416

Large Intestine Billions of anaerobic bacteria break down material further, producing vitamins (B 12, K) Main function is to absorb water (~90%) The leftover matter forms feces which are pushed by muscular contractions (peristalsis again!) into the rectum and out the anus through the anal sphincter. Ascending Transverse Descending Rectum Anus Sigmoid

Liver Gall Bladder Stomach Pancreas Small Intestine Large Intestine Accessory Organs & The Digestive Tract Rectum Anus Digestive Organs Accessory Organs Esophagus

How long does it take? Digestion time varies depending on the individual For healthy adults, it's usually between 24 and 72 hours After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine Elimination of undigested food residue through the large intestine usually begins after 24 hours

Digest this! Mouth Esophagus Liver Stomach Pancreas Large Intestine Small Intestine Duodenum Sphincters Jejunum Ileum Transverse colon Ascending colon Descending colon Peristalsis occurs here… Gallbladder Anus Salivary glands HCL Pepsin Bile Amylase

Digest this! 1.Trace the torso of a teammate on the chart paper provided 2.Using as many words from the board as you can, draw and label the organs of the digestive system as best you can. 3.Clearly label where mechanical and chemical digestion occur 4.Add in digestive enzyme…

HW Section 10.2: Pages Fill out handout Questions: Pg #17, 18 Pg #2, 3, 5, 6, 10, 12