Biology Ch. 6

Front 1

Digestion

Back 1

-the breakdown of ingested foods before they are absorbed into the body.

Front 2

Basic anatomy of the digestive tract

Back 2

mouth, esophagus, stomach, small intestine, large intenstine, rectum, anus.

Front 3

alpha-amylase

Back 3

-enzyme that begins breaking down the long straight chains of starch into polysaccharides in the mouth.

Front 4

Esophagus

Back 4

-After food is chewed in the mouth, it forms a bolus which is pushed down the esophagus via peristaltic action.
-no digestion occurs in the esophagus.

Front 5

Chyme

Back 5

a semifluid mass produced by the stomach from food.

Front 6

Stomach

Back 6

-a very flexible pouch that both mixes and stores food.
-reduces food to chyme
-contains exocrine glands
-begins protein digestion with the enzyme pepsin.
-the low pH of the stomach assists in the process of protein digestion by denaturing the proteins.

Front 7

The four major cell types in the stomach

Back 7

1. mucous cells
2. chief (peptic) cells
3. parietal (oxyntic) cells
4. G cells

Front 8

Mucous cells

Back 8

-secrete mucus
-mucus is composed mostly of sticky glycoprotein and electrolytes
-functions to lubricate the stomach wall so that food can slide along its surface without causing damage.
-protects the epithelial lining from the acidic environment.

Front 9

Chief cells

Back 9

-secrete pesinogen, the zymogen precursor to pepsin.
-pepsin begins protein digestion when activated by HCl

Front 10

Pepsinogen

Back 10

-the zymogen precursor to pepsin.
-secreted by chief cells in the stomach.

Front 11

pepsin

Back 11

-an enzyme secreted by Chief cells in the stomach which begins protein digestion.
-the zymogen precursor pepsinogen is activated by low pH

Front 12

Parietal cell

Back 12

-found in the exocrine glands of the stomach
-secrete HCl which diffuses into the lumen
-the hydrogen from the HCl is expelled into the lumen side of the cell while the bicarbonate ion is expelled into the interstitial fluid side
-net result is to lower the pH of the stomach, raise the pH of the blood.

Front 13

G cells

Back 13

-located in the stomach
-secrete Gastrin into the interstitium, which is absorbed by the blood and stimulates parietal cells to secrete HCl

Front 14

Gastrin

Back 14

-a large peptide hormone secreted by G cells in the interstitium of the stomach.
-absorbed into the blood, stimulates parietal cells to secrete HCl.

Front 15

Small intestine

Back 15

-responsible for 90% of digestion and absorption
-the outermost layer is lined with finger-like projections called villi
-the villi increase the surface area of the intestinal wall

Front 16

Villi

Back 16

-finger like projections that line the wall of the small intestine
-serve to increase the surface area of the intestinal wall allowing for greater digestion and absorption
-Within each villus is a capillary network and a lymph vessel called a lacteal
-Nutrients absorbed through the wall pass into the capillary network and the lacteal

Front 17

Lacteal

Back 17

-a lymph vessel located within each villus in the small intestine

Front 18

Microvilli

Back 18

-On the apical (lumen side) surface of the cells of each villus are much smaller fingerlike projections called microvilli
-increase the surface area even more

Front 19

Brush border

Back 19

-fuzzy covering in the small intestine that contains membrane bound digestive enzymes, such as carbohydrate-digesting enzymes, peptidases, and nucleosidases

Front 20

Goblet cells

Back 20

-epithilial cells that secrete mucous to lubricate the intestine and help protect the brush border from mechanical and chemical damage.

Front 21

Pancreas

Back 21

-secretes bicarbonate ions into the duodenum, increasing the pH to 6
-an exocrine gland, releases enzymes as zymogens.

Front 22

Major enzymes released by the pancreas

Back 22

1. trypsin
2. chymotripsin
3. pancreatic amylase
4. lipase
5. ribonuclease
6. deoxyribonuclease

Front 23

Trypsin and chymotripsin

Back 23

-enzymes secreted by the pancreas that degrades proteins into small polypeptides
-this way, proteins reach the brush border in the small intestine as small polypeptides where they are reduced further before absorption

Front 24

Pancreatic amylase

Back 24

-hydrolizes polysaccharides to disaccharides and trisaccharides
-more powerful than salivary amylase
-degrades nearly all carbs from chyme into small glucose polymers

Front 25

Lipase

Back 25

-an enzyme secreted by the pancrease that degrades fat, specifically triglycerides

Front 26

Bile

Back 26

-A fluid produced by the liver and stored in the gall bladder
-emulsifies fat, or breaks it up into small particles without changing it chemically.
-does this because fat clumps together in the aqueous solution, reducing surface area.
-lipase can now more easily degrade it.

Front 27

Gal bladder

Back 27

-Stores bile that is produced by the liver.

Front 28

Large intestine

Back 28

-Major function is water absorption and electrolyte absorption
-contains E. coli

Front 29

Carbohydrate digestion

Back 29

-Glucose is absorbed in the intestine by a secondary active transport mechanism down the concentration gradient of sodium
-when cells have reached the saturation point with glycogen, carbs are converted to fatty acits and then triglycerides in a process requiring a small amount of energy.
-the glucose enters the blood stream and goes to the liver where it is converted to glycogen. Most cells can convert glucose to glycogen and store some, but large stores are only in muscle and liver.

Front 30

Protein absorption

Back 30

-absorption occurs via cotransport mechanism down the concentration gradient of sodium, similar to the mechanism used by glucose.
-polypeptides are absorbed into an enterocyte and hydrolyzed to their amino acid constituents.
-build proteins, when need break them down and transport them to blood.

Front 31

Urea

Back 31

-nearly all ammonia is converted to urea by the liver and then excreted in the urine by the kidney.

Front 32

Fat absorption and storage

Back 32

-triglycerides are broken down into monglycerides and fatty acids before they are shuttled to the brush border by bile micelles and diffuse through the enterocyte membrane.
-Once inside the enterocyte, turned back into fat by smooth ER.
-then move into the lacteals.

Front 33

Albumin

Back 33

-a molecule that transports fatty acids.
-From adipose tissue, most fatty acids are transported in the form of free fatty acid which combines immediately in the blood with albumin.

Front 34

Functions of the liver

Back 34

1. Blood storage-liver can expand to act as a blood reservoir for the body.
2. Blood filtration-Kupfer cells phagocytize bacteria picked up from the intestines
3. Carbohydrate metabolism- liver maintains normal blood glucose levels through gluconeogenesis, glycogenesis, and storage of glycogen
4. Fat metabolism- synthesizes bile from cholesterol and converts carbs and proteins to fat. Oxidizes fatty acids and forms lipoproteins
5. Protein metabolism-deaminates amino acids, forms urea from ammonia in the blood, synthesizes plasma proteins such as fibrinogen, prothrombin, albumin, and most globulins, synthesizes nonessential amino acids.
6. Detoxification-detoxified chemicals are excreted by the liver as part of bile or polarized so they may be excreted by the kidney
7. Erythrocyte destruction-destroys irregular erythrocytes
8. Vitamin storage-stores vitamins, stores iron combining it with protein

Front 35

Functions of the kidneys

Back 35

1. to excrete waste products, such as urea, uric acid, ammonia, and phosphate
2. to maintain homeostasis of the body fluid volume and solute composition
3. to help control plasma pH

Front 36

Nephron

Back 36

-the functional unit of the kidney

Front 37

Glomerulus

Back 37

-The first capillary bed of the nephron in the kidney
-hydrostatic pressure forces some plasma through the glomerular epithelium and into the Bowman's capsule
-the fenestrations screen out white blood cells and large proteins

Front 38

Bowman's capsule

Back 38

-along with the glomerulus, forms the renal corpuscle in the nephron of the kidney

Front 39

Renal corpuscle

Back 39

-formed from the glomerulus and the Bowman's capsule.
-located in the nephron of the kidney

Front 40

Proximal tubule

Back 40

-filtrate (fluid filtered through the glomerulus) moves from the bowman's capsule to the proximal tubule in the nephron.
-the location of most reabsorption in the kidney
-secondary active transport proteins in the proximal tubule are responsible for reabsorption of nearly all glucose, most proteins, and other solutes.
-Drugs, toxins and other solutes are secreted into filtrate by cells of the proximal tubule
-Hydrogen ions are secreted through an antiport system. which is driven by the sodium concentration gradient.
-net result is to reduce the amount of filtrate in the nephron while changing the solute composition without changing the osmolarity.

Front 41

loop of Henle

Back 41

-from the proximal tubule, the filtrate flows into the loop of Henle of the kidney nephron.
-function is to increase the solute concentration, and thus the osmotic pressure, of the medulla.
-water passively diffuses out of the loop of Henle and into the medulla.
-descending low permeability to salt- osmolarity increases.
-ascending loop is nearly impermeable to water, actively transports Na in order to create a high osmolarity in the medulla.

Front 42

Distal tubule

Back 42

-after proceeding through the loop of Henle, flitrate passes through the distal tubule of the kidney nephron.
-reabsorbs Na, Ca, secretes K, H, HCO3.
-aldosterone acts on the distal tubule cells to increase Na and K membrane transport proteins
-net effect is to LOWER filtrate osmolarity.

Front 43

Collecting duct

Back 43

-At the end of the distal tubule in the kidney nephron.
-carries the filtrate into the highly osmotic medulla.
-impermeable to water but sensitive to ADH
-in the presence of ADH, the collecting duct becomes permeable to water allowing it to passively diffuse into the medula, concentrating the urine.

Front 44

juxtaglomerular apparatus

Back 44

-moniters filtrate pressure in the distal tubule
-specialized cells secrete the enzyme renin, which initiates a regulatory cascade producing angiotensin I,II, and II, which ultimately stimulates the adrenal cortex to secrete aldosterone.