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Powerpoint Presentation: Digestion

 

Animal Physiology Index

The Nervous System and Movement
Muscle contraction
The Nerve Impluse
The Synapse
The Major Factors controlling the Heartbeat
Defence Against Disease
Reproduction
Digestion

Topic Chapters Index

 

ANIMAL PHYSIOLOGY

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The Alimentary Canal or Gut

Region

Features

Functions

Mouth/ Pharynx

Specialised teeth + jaws

Mastication

Tongue, taste buds

Taste + bolus (food lump) formation

Salivary glands (3 pairs)

 

Amylase

Starch hydrolysis

Hydrogen carbonate

Alkaline pH

Water

Lubrification + solvent

 

 

 

Oesophagus
(20s)

Muscular tube (circular & longitudinal muscles)

Peristaltic waves moves the bolus along

Mucus epithelium

Lubrication

 

 

 

Rumen
(ruminants only)

Compartmentalized sack

Bacterial fermentation of cellulose

 

 

 

Stomach

(transit 0 to 3h)

(capacity 1.5dm3)

Muscular sack (Circular, longitudinal. & diagonal muscles)

Churning food into chyme

Gastric Pits:

 

HCl

Acidic pH: Enzyme activation & bacteriocidal

Pepsinogen (inactive)→ Pepsin (active)

Protease

Rennin

Milk → Curds (coagulates casein)

Lipase

Lipid hydrolysis

Mucus epithelium → mucus

Protection of stomach from acid and protease enzymes

Gastrin (hormone) & Vagus nerve

Control gastric juice secretion

Cardiac sphincter & pyloric sphincter (muscular valves)

Hold food in stomach for digestion

 

Only alcohol and some salts are absorbed by the stomach wall

     

Small Intestines

Duodenal wall: Hormones Secretin and Pancreozymin:

Control pancreatic juices

Glands: Enzymes (e.g. lactase) Enterokinase

Disaccharide digestion

Activates trypsin

Duodenum
(25cm)

Jejunum & Ileum

( transit 1.5h)

Length (3 5m long), Rugae (folds), Villi & Microvilli

Large surface area 200m2 (total small intestine)

(a) Digestion membrane bound enzymes.

(b) Absorption.

Capillaries

Transport of digested food.

Lacteals (lymph vessels)

Fatty acids + monoglycerides.

Hepatic portal system

All absorbed food is first taken to the liver for processing and regulation

Gut flora (bacteria)

Mutualistic & vitamin synthesis

 

 

 

Liver

Bile duct → Bile

Emulsifies fats

Hepatic portal system

All absorbed food is first taken to the liver for processing and regulation

 

 

 

Pancreas

Pancreatic duct

 

(a) Hydrogen carbonate

Neutralizes stomach acid Alkaline pH activates enzymes.

(b)Enzymes

 

Trypsin

protease

Amylase

hydrolyses starch

Lipase

hydrolyses lipids

RNAase and DNAase.

Nucleic acid digestion

 

 

 

Large Intestine
(transit up to 96h)
(1,5m)

 

 

Caecum/ Appendix

Sack at the beginning of the large intestine

Bacterial fermentation cellulose (non ruminants)
Vestigial in humans.

Colon

No villi but rugae (folds)

Water absorption

Bacterial activity

Mutualistic

Rectum

Anal sphincter

Holding area for faeces before egestion.

 

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