Human Anatomy & PhysiologyDIGESTIVE & EXCRETORY

SYSTEMS

Biology – Chapter 381

Primary Function

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Convert foods into simpler molecules that the body can absorb and be used by cells

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What & why do we need to eat?

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Nutrients – supply energy and raw materials for body to perform life functions

Water – all chemical reactions in your body require water

Carbohydrates – the main source of energy

Fats – helps produce membranes, myelin, some hormones

Proteins – raw materials for growth & repair, enzymes

Vitamins – organic molecules that help regulate body processes

Minerals – inorganic nutrients needed for bodily functions

Anatomy of Digestion

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Digestive System Primary Organs:

Mouth, Pharynx, esophagus, stomach, small intestine, large intestine

Accessory organs (add secretions to aid digestion):

salivary glands, pancreas, liver

Mouth & Salivary Glands

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Primary function: Break down, moisten food & start chemical digestion (mechanical and chemical digestion)

Teeth – mechanical digestion

Salivary glands – produce amylase to start chemical digestion

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Pathways in the Mouth

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Back of mouth (pharynx) leads to TWO tubes:Esophagus (empties into stomach)Trachea (leads to lungs)

DON’T want food to clog trachea!

Direction controller = epiglottis

The Esophagus

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Tube connecting the mouth and the stomach

Tongue and throat push chewed, moistened food (bolus) past the epiglottis into the esophagus

Bolus is moved through esophagus by involuntary muscular contractions (peristalsis)

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The Stomach

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The bolus is mechanically (churning) and chemically digested in the stomach

Chemical digestion:HClPepsin

Produces Chyme

Pushed through pyloric valve to small intestine

Small Intestine

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Anatomy:3 parts-Duodenum-Jejunum-Ileum-Villi

Function:-Location where most food is digested & absorbed

Accessory organs:-Pancreatic enzymes (Starch, protein, fat)-Liver enzymes (Bile-fat digestion, stored in gall bladder)

Villi

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Villi greatly increase small intestine surface area for more effective absorption (can cover an area as large as a tennis court)Undigested substances (cellulose, water, etc.) leave small intestine & move to large intestine

Large Intestine

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Anatomy: -Ascending colon-Appendix-Transverse colon-Descending colon

Primary Function:-Reabsorb water

Waste material passed to rectum (storage, bacterial colonies produce organic nutrients)

Excess waste released through anus

Digestion Summary

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Excretory System

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Anatomy:SkinLungsLiverKidneys

Primary functions:Maintain homeostasisRemove toxic chemicals

Liver

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Converts excess amino acids (from protein digestion) into useful nutrients, producing nitrogenwaste products (urea)Passed on to kidneys

Kidneys

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Two kidneys in lower backFilter blood to remove waste products

Ureters connect to urinary bladder - removed through urethra

Kidney Anatomy:-Nephron-Filters out toxic waste-Reabsorbs water, essential nutrients

Dialysis

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