Class Notes (834,721)
Canada (508,692)
ANSC 3120 (39)
c (6)

3. Digestion and Digestive System.doc

12 Pages
Unlock Document

Animal Science
ANSC 3120

Digestion and Digestive Systems Digestive Tract 1. Mouth 2. Esophagus 3. Stomach  Single  Multiple 4. Small Intestine Associated glands and organs  Duodenum  Salivary glands  Jejunum  Liver  Ileum  Gall bladder 5. Caecum  pancreas 6. Large Intestine 7. Rectum, Anus Killing, Killing, Tearing Tearing, Chewing Tearing, Chewing Tugging Tearing, Pecking Grinding 1. 1. Simple System Digestion and Digestive System1  Human, monkey, pig, dog (omnivores), cat (carnivore) o Mongastric – “single stomach” o Require rich nutrient diet due to nature of the GI tract o The caecum only contribute 1% – 2% of fermentation capacity  May provide a reservoir of bacteria to reseed colon  Untreated appendicitis can be fatal (evolution?)  Small increase in Crohn’s Disease after appendectomy o Require a relatively nutrient-dense and digestible diet o Humans can obtain as much as 15% (in reality, 5% with today’s diet) of their energy requirement from VFA production on a high fibre diet (like hunters, gatherers)  Mouth: chewing, saliva o Salivary amylase o Structure suited to diet Esophagitis “acid reflux” o Starch is digested to glucose (sweet!) -itis = inflammation Relaxed sphincter  Esophagus: smooth muscle Chocolate o ~ 10sec to swallow bolus of food and smoking can cause the  Stomach: Secretions sphincter to o HCl; lowers pH to ~ 2 relax HCl  Denatures dietary protein  Kills most bacteria o Pepsinogens (activated by HCl)  Pepsinogen  pepsin  Protein digestion o Mucus/bicarbonate  Protect epithelium o Gastrin, cholecystokinin (CCK), other regulatory peptides Digestion and Digestive System 2  Control motility, sphincters and secretions o Intrinsic factor (for Vitamin B 12  More on this later o Chyme  Semifluid mass of acidic partly digested food expelled by the stomach into the duodenum  Small Intestine: Secretions; o Bicarbonate (HCO ), increases the pH to 8-9 3 o Secretions from pancreas and gall bladder (bile) are also alkaline o Pancreas is very important in digestion Gall stones  Pancreatic secretions also include “ouch” various enzymes involved in CHO, protein and fat digestion o Bile (bile acid/salts, various lipids, bicarbonate) is made in the liver stored in the gall bladder and secreted into the duodenum Gall stone “death” or extreme pain X X X X  Massive folding increases surface area for optimal rate of nutrient absorption  Microvilli comprise the brush border membrane  Small intestine length is roughly 5 m with a diameter of 3cm Submucosal folds 2  Surface area increased 500X  200 m (tennis court) Digestion and Digestive System 3  Surface Area is increased by : 1. Submucosal folds  Large folds under mucosa, protrude into lumen (see previous slide) 2. Villi  Mucosa folds into villi, finger-like projections into lumen 3. Microvilli  Tiny projections of plasma membrane on the surface of each mature mucosal cell  The microvilli are in turn coated with a furry layer of polysaccharides and glycoproteins called the glycocalyx  The microvilli and glycocalyx together are called the “brush border” o Site of nutrient absorption o Small intestine is usually 3X longer than large intestine (colon) o “small” refers to the diameter  Large Intestine  Water, Na, Cl, K absorption  Bacteria produce many vitamins and amino acids, of which few are available for absorption (eg biotin & vitamin K)  Vitamin K is lipid soluble and absorbed by diffusion  1 billion micro-organisms per mL digesta  Lots of fermenatation • Fibre  bacteria  glucose • An anaerobic process Pyurvate  Produces Volatile Fatty Acids (VFAs)  Why? Colon Ecology  We do not express transporters in colon for sugars, amino acids, mineral and most vitamins  To allow for bacteria to “condition” the colon environment Digestion and Digestive System 4 Passive transport 4% 40% 5 m Decreasing 56% villus density Active transport 1.5 m  Transporters are expressed in locations that match
More Less

Related notes for ANSC 3120

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.