Animal Structure and Function Digestive Circulatory and Respiratory Excretory Nervous Muscular Endo, repro, develop Immune

DIGESTIVE SYSTEM

“tube within a tube” This

“tube within a tube” Develops from this

Coelom and germ layers

Don’t be grossed out but… ECTODERM DIGESTIVE TRACT (inside tube) MESODERM ENDODERM

Purpose for digestive system To break down food into useable nutrients that can be absorbed and transported to cells throughout body Remember – we are heterotrophs!

We need… water, salts Vitamins and minerals – to maintain overall health Macromolecules Carbs for energy Proteins for building and repairing of tissues Lipids for stored energy source, brain development (babies), essential for fat-soluble vitamins

ANATOMY- know pathway food travels

PHYSIOLOGY of human digestive tract Two main parts Alimentary canal – the tube or pathway that the food travels through Accessory glands – outside of the “tube” but aid in digestion by secreting enzymes into the tract

Accessory glands Fill in the enzymes they secrete as we go through the whole process Salivary gland – Pancreas – Liver – Gall bladder –

Oral Cavity – physical (teeth grinding) and chemical digestion (saliva) Saliva = key enzyme is amylase which breaks down starch and glycogen into smaller carbs and maltose also contains: mucin (glycoprotein to protect lining of mouth) buffers and antibacterial agents

Pharynx Pharynx – passageway for both air into lungs and food into esophagus epiglottis – blocks trachea when swallowing so bolus (food ball) enters the esophagus

Esphagus peristalsis starts here bolus must pass through the esophageal sphincter

Stomach gastric juice pepsin mucous

Small Intestines – the main player

Inside lining of Small Intestine MAJOR SURFACE AREA FOR MAJOR ABSORPTION!

Enzymes secreted into S.I.- you tell me their functions pancreatic amylases from the pancreas disaccharidases from the lining trypsin and chymotrypsin from the pancreas exopeptidases from intestinal lining lipase from the pancreas http://www.biologyinmotion.com/bile/index.html bile from the gall bladder

Control of pancreatic enzymes Why secrete the inactive forms? Trypsinogen Chymostrypsinogen HINT: once activated they break down proteins and your tissues contain a lot of…

Asorption of nutrients in the small intestine capillaries receive – carbohydrates and proteins Nutrient rich blood from S.I. is carried via hepatic portal vessel to the liver Liver is in charge of distributing nutrients to blood (and rest of body

Asorption of nutrients in the small intestine Lacteals receive – packaged lipids These lead to the lymphatic system which carries the lipids to the heart

Large Intestine water reabsorption salt excretion - if salt content is too high in blood eliminate undigested food- feces formation and elimination

Large Intestine

Reclaiming Water in The L.I. If lining of LI is infected with bacteria or virus – water unable to be reabsorbed so fecal material is watery = diarrhea If too much water is reabsorbed or sluggish peristalsis = constipation

Radiological Images of GI Tract http://www9.biostr.washington.edu/hubio511/RadAbdo/

Homeostasis and Control of Digestive System Nervous system Smelling, tasting and seeing (hearing the sizzle?) all stimulate the secretion of gastric juices

Negative feedback Gastrin is secreted when food is present in the stomach Gastrin increases the secretion of gastric juices When the pH gets too low – gastrin secretion stops which in turn slows down gastric juice production (which caused the pH to lower in the first place)

Hormonal Control PANCREAS bicarbonate SECRETIN

Hormonal Control Bile Pancreatic Enzymes CCK

Comparative Physiology

HERBIVORE OR CARNIVORE?

Who’s GI Tract? Check text

The End! Oh the pictures I could have put on this last slide!