ch 38-2 the process of digestion

CH 38-2 THE PROCESS OF DIGESTION

By the end of this section you should be able to: Identify the organs of the digestive systemDescribe the function of the digestive system


alimentary canal – one-way tube that passes through the body


digestive system – helps convert foods into simpler molecules that can be absorbed and used by the cells of the body


– includes: mouth pharynx esophagus small intestine large intestine stomach


accessory structures: add secretions to the digestive system pancreas liver salivary glands

CH 38-2 THE MOUTH

mechanical digestion – physical breakdown of large pieces of food into smaller pieces

CH 38-2 THE MOUTH

chemical digestion – breakdown of large food molecules into smaller food molecules with digestive enzymes

CH 38-2 THE MOUTHmouth – the organ in which digestion beginsteeth – tear and crush food into a fine paste until it is ready to be swallowed – anchored to the bones of the jaw; protected by a coating of enamel – do much of the mechanical digestion

CH 38-2 THE MOUTH

saliva – secreted by salivary glands as the teeth cut and grind food – secretion is controlled by the nervous system; can be triggered by scent

CH 38-2 THE MOUTHthree functions:1) helps to ease the passage of food through the digestive system by moistening food2) contains lysozyme – an enzyme that fights infection by digesting the cell walls of bacteria that enter the mouth3) contains amylase – begins to break the bonds in starches to produce simpler sugars

CH 38-2 THE ESOPHAGUSbolus – chewed clump of food that is pushed down the throat by the tongue and throat muscles epiglottis – flap of tissue that covers the trachea when swallowing to prevent food from entering lungs

CH 38-2 THE ESOPHAGUSesophagus – tube that connects the throat (pharynx) to the stomach– walls are made of ringed muscle that squeeze food through the tube– peristalsis – the rhythmic muscular contractions of the smooth muscle in the digestive system that pushes food along

CH 38-2 THE ESOPHAGUScardiac sphincter – also called esophageal sphincter– a thick ring of muscle that closes the esophagus after food has passed into the stomach– prevents the contents of the stomach from moving back into the esophagus

CH 38-2 THE ESOPHAGUS

heartburn – backflow of stomach acid across the cardiac sphincter– can be caused by overeating, overdrinking, or excess caffeine

CH 38-2 THE STOMACHstomach – large, muscular sac just below the diaphragm in the abdomen– three layers of smooth muscle– churns and mixes the food that is swallowed

CH 38-2 THE STOMACH

chemical digestion – stomach is lined with millions of microscopic gastric glands that release a number of substances into the stomach

CH 38-2 THE STOMACHgastric secretions include:1) mucus – lubricates food and protects the stomach lining 2) HCl – hydrochloric acid makes the stomach contents acidic which allows pepsin to work

CH 38-2 THE STOMACHgastric secretions include:3) pepsin – enzyme that begins the digestion of protein– works best in acidic environments– breaks proteins into smaller polypeptide fragments

CH 38-2 THE STOMACH

the acidic environment denatures (“changes the shape of”) the amylase enzyme, so carbohydrate digestion stops in the stomach (it restarts in the small intestine)

CH 38-2 THE STOMACHmechanical digestion – muscular walls of the stomach contract to churn and mix stomach fluids and food to produce chyme▫ chyme – a pasty mixture of food that results after 2 to 3 hours of churning in the stomach

CH 38-2 THE STOMACH

pyloric valve – a ring of muscle between the stomach and small intestine – opens to allow chyme to flow into the small intestine

CH 38-2 THE STOMACH

CH 38-2 THE SMALL INTESTINE

The Small Intestinethree sections: 1) duodenum 2) jejunum 3) ileum

CH 38-2 THE SMALL INTESTINEduodenum – first of the three parts of the small intestine– where almost all of the digestive enzymes enter the intestines– chyme mixes with enzymes and digestive fluids from the pancreas, liver, and the lining of the duodenum

CH 38-2 THE SMALL INTESTINEintestinal secretions1) peptidase – breaks down dipeptides into amino acids 2) maltase, sucrase, and lactase – breaks down remaining disaccharide into monosaccharides

CH 38-2 THE SMALL INTESTINEaccessory structures: pancreas – long gland located behind the stomach– gland that serves three functions:1) produces hormones that regulate blood sugar levels 2) produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids


3) produces sodium bicarbonate to neutralize HCl from stomach acid – because pancreatic enzymes only work in a neutral environment

CH 38-2 THE SMALL INTESTINEliver – large, brownish organ located just above and to the right of the stomach– secretes bile – yellow-brown liquid loaded with lipids and salts – acts like a detergent - breaks fat into smaller and smaller droplets which make it possible for enzymes to reach more surface area


gallbladder – pouch-like organ behind the liver that stores bile

CH 38-2 ABSORPTION IN THE SMALL INTESTINE

jejunum and ileum – last two sections of the small intestine– approximately 6 meters long– at this point chemical digestion is complete


– nutrient molecules are absorbed from these two sections into the bloodstream – peristalsis move the chyme along the jejunum and ileum


villi – finger-like projections that increase the surface area of the walls of the small intestine


microvilli – thousands of even tinier finger-like projections found on the surface of the cells of the villi!– inside each villus is a network of capillaries and lymph vessels

CH 38-2 ABSORPTION IN THE SMALL INTESTINEabsorption – nutrients are absorbed into the cells of the villi lining the small intestine– carbohydrates and proteins are absorbed into capillaries– undigested fat and some fatty acids are absorbed into lymph vessels


when food leaves the small intestine, it is nutrient-freeonly water, cellulose, and other undigestible substances remain


appendix – small sac-like organ in small intestine that does little to promote digestion– can be clogged and inflamed - appendicitis

CH 38-2 THE LARGE INTESTINElarge intestine, or colon – removes water from undigested material that is left– bacterial colonies produce compounds like vitamin Kconcentrated waste material passes through the rectum and is eliminated

CH 38-2 DIGESTIVE SYSTEM DISORDERS

GERD – gastroesophageal reflux disease – chronic heartburn in 25-35% of people– symptoms – heartburn, regurgitation, difficulty swallowing


causes – defects in esophageal sphincter; – slower than normal emptying of the stomach; – decreased secretion of bicarbonate by the esophagus – treatments – lifestyle changes; medication to control stomach acid; surgery


peptic ulcer – hole in stomach lining produced by the powerful acids released into the stomach – most are caused by Heliobacter pylori; can be cured with antibiotics

CH 38-2 DIGESTIVE SYSTEM DISORDERSdiarrhea – irritation or infection that interferes with the removal of water from the large intestines

CH 38-2 DIGESTIVE SYSTEM DISORDERSconstipation – condition resulting from the removal of too much water from the undigested material in the large intestine

CH 38-2 THE PROCESS OF DIGESTIONBy the end of this section you should be able to: Identify the organs of the digestive systemDescribe the function of the digestive system

CH 38-2 THE PROCESS OF DIGESTIONIdentify the organs of the digestive systemMouth, pharynx, esophagus, stomach, small intestine, and large intestine

Describe the function of the digestive system

CH 38-2 THE PROCESS OF DIGESTIONDescribe the function of the digestive systemTo convert food into simple molecules that can be absorbed and used by the cells of the body

CH 38-3 THE EXCRETORY SYSTEMBy the end of this section you should be able to:Describe the functions of the kidneys

Explain how blood is filtered

CH 38-3 FUNCTIONS OF THE EXCRETORY SYSTEMexcretion – process by which metabolic wastes are eliminated– maintains homeostasis in the internal cellular environment– rids the body of excess salt, CO2 and urea– urea – toxic compound that is produced when amino acids are used for energy

CH 38-3 THE EXCRETORY SYSTEMorgans of excretion 1) skin – excretes excess water and salt, and a small amount of urea in sweat2) lungs – excrete carbon dioxide that is produced when ATP is made

CH 38-3 THE EXCRETORY SYSTEM3) liver – takes up amino acids from proteins that have been broken down– converts the amino acids into other useful compounds– produces nitrogen waste in the process, which is potentially poisonous– the liver converts this nitrogen waste quickly to urea – urea is removed from the bloodstream by the kidneys

CH 38-3 THE EXCRETORY SYSTEM4) kidneys – play an important role in maintaining homeostasis by...1) removing waste products from the blood2) maintaining blood pH3) regulating the water content of the blood (i.e., blood volume)

CH 38-3 THE KIDNEYS

anatomy of excretion kidneys – located on either side of the spinal column near the lower back

CH 38-3 THE KIDNEYS

ureter – tube that leaves each kidney carrying urine to the urinary bladder– maintains homeostasis in the internal cellular environment

CH 38-3 THE KIDNEYS

urinary bladder – sac-like organ in which urine is stored before being excreted

CH 38-3 THE KIDNEYS

CH 38-3 THE KIDNEYS function of kidney 1) blood enters the kidney through the renal artery2) kidneys remove urea, excess water and other waste products from the blood

CH 38-3 THE KIDNEYS

3) waste products are passed on to the ureter4) clean, filtered blood leaves the kidney through the renal vein to return to circulation

CH 38-3 THE KIDNEYSkidney structure – 10 cm long, 6 cm in diameter two distinct regions:1) renal medulla – inner part of the kidney2) renal cortex – outer part of the kidney

CH 38-3 THE KIDNEYSKidney Nephron

Cortex

Medulla Renal artery

Renal vein

Ureter

To the bladder

Bowman’s capsule

Glomerulus

Capillaries

Collecting duct

To the ureter

Loop of Henle

Artery

Vein

CH 38-3 THE KIDNEYSnephrons – functional units of the kidney; small independent processing units– 3 cm long, 0.03 mm wide; 1 million per kidney!– located in the renal cortex except for the loop of Henle which extends into the renal medulla

CH 38-3 THE KIDNEYS

– each nephron has one arteriole and one venule with a network of capillaries connecting them– releases fluid to the collecting duct that leads to the ureter

CH 38-3 THE KIDNEYS▫ flow of blood through nephron – to purify blood1) blood enters the nephron through the arteriole2) impurities are filtered out and emptied into the collecting duct3) purified blood exits the nephron through venule

CH 38-3 THE KIDNEYS

blood purification – requires two processes:1) filtration2) reabsorption

CH 38-3 THE KIDNEYS

FiltrationMost filtration occurs in the glomerulus. Blood pressure forces water, salt, glucose, amino acids, and urea into Bowman’s capsule. Proteins and blood cells are too large to cross the membrane; they remain in the blood. The fluid that enters the renal tubules is called the filtrate.

ReabsorptionAs the filtrate flows through the renal tubule, most of the water and nutrients are reabsorbed into the blood. The concentrated fluid that remains is called urine.

CH 38-3 THE KIDNEYS

filtration – the process of passing a liquid or a gas through a filter to remove waste– takes place in the glomerulus

CH 38-3 THE KIDNEYS

glomerulus – a small network of capillaries encased in the upper end of the nephron by a hollow structure called Bowman's capsule

CH 38-3 THE KIDNEYS

reabsorption – the process in which liquid is taken back into a vessel– most of the material removed from the blood at Bowman's capsule is returned to the blood

CH 38-3 THE KIDNEYSSteps to blood purification in the nephron:1) the blood is under pressure and the walls of the capillaries and Bowman's capsule are permeable2) fluid flows from the blood into Bowman's capsule; this fluid is called filtrate

CH 38-3 THE KIDNEYS3) filtrate contains: water glucose amino acids some vitamins salts urea filtrate does not contain: cells plasma proteins platelets (because they are too large to filter out)

CH 38-3 THE KIDNEYS4) amino acids, fats and glucose are actively pumped out of filtrate and reabsorbed by the capillaries – water follows by osmosis 5) filtrate (with little water or nutrients left) drains into collecting ducts

CH 38-3 THE KIDNEYS6) urine – the remaining filtrate; contains urea, excess salt and water– empties into a collecting duct– becomes concentrated (excess water is reabsorbed) in the loop of Henle– loop of Henle - the section of nephron tubule in which water is conserved and volume of urine is minimized

CH 38-3 THE KIDNEYS

7) urine is stored in the urinary bladder until it can be released from the body through a tube called the urethra

CH 38-3 THE KIDNEYSdrugs in urine – drugs are not usually reabsorbed, they remain in the filtrate and are eliminated in the urine– this is why the effects of many drugs wear off over time (e.g., antibiotics)

CH 38-3 THE KIDNEYS

– this also means that drugs become more concentrated in the urine, so a urine test is a quick, easy way to test for illegal drugs

CH 38-3 THE KIDNEYS

kidney stones – calcium, magnesium, and uric acid salts can crystallize and form a block in the ureter

CH 38-3 THE KIDNEYS – cause severe pain – treated with ultrasound waves to pulverize the stone into small fragments that can be eliminated through the urethra

CH 38-3 THE KIDNEYSControl of Kidney Functionactivities of the kidney are controlled by:1) the composition of the blood itself2) regulatory hormones released in response to composition of blood

CH 38-3 THE KIDNEYSexample – when you drink a glass of water...1) the amount of water in your blood increases2) the rate of water reabsorption decreases3) less water is returned to the blood4) excess water is sent to the urinary bladder to be excreted

CH 38-3 THE KIDNEYSexample – when you eat salty food...1) the amount of salt in your blood increases2) the kidney allows less salt to be reabsorbed into the blood3) excess salt is excreted in the urine

CH 38-3 THE KIDNEYS

Homeostasis by Machine- humans have two kidneys, but can live with one- if both kidneys are damaged, there are two alternatives:

CH 38-3 THE KIDNEYS

1) kidney transplant – from a compatible donor

CH 38-3 THE KIDNEYS2) kidney dialysis – if no donor is availablea) blood is removed from the body through a tube, and is sent through a series of tubing that acts like a nephronb) holes in the tubing allow salt and small molecules to pass through

CH 38-3 THE KIDNEYSc) waste, urea, and excess salt diffuse out of the blood into a fluid filled chamberd) purified blood is returned to the body▫ dialysis is expensive and time-consuming (several hours, 3 times/week)

CH 38-3 THE KIDNEYS

Air detector Dialysis machine

Blood pump

Blood in tubing flows through dialysis fluid

Used dialysis fluid

Compressed air

Fresh dialysis

fluid

CH 38-3 THE EXCRETORY SYSTEMBy the end of this section you should be able to:Describe the functions of the kidneys


CH 38-3 THE EXCRETORY SYSTEMDescribe the functions of the kidneysRemove waste products from the blood; maintain blood pH; and regulate the water content of the blood (blood volume)Explain how blood is filtered

CH 38-3 THE EXCRETORY SYSTEM


ch 38-2 the process of digestion

Documents

process of digestion

digestive system ch

crush food

food alongch

passage of food

clump of food

smaller food molecules

body ch