A&P II Lecture Ch24 Part B

Left lobe & right lobe

2 major lobes of the liver

Porta hepatis

Where vessels, ducts, nerves, exit/enter liver

two hepatic ducts (Right & Left)

Bile exits the liver via

portal vein, hepatic artery, bile duct

Portal triad vessels include:

in center of lobule.

Central vein location

Gallbladder

Saclike structure for bile storage.

Cholecystokinin (CCK) (from the intestine) and vagal stimulation.

cystic duct then into common bile duct

Bile exits through

Gallstones

precipitated excess cholesterol

common hepatic duct

Right & left hepatic ducts unite to form

common bile duct

Cystic duct from gallbladder joins common hepatic duct to form the

Bile salts

Emulsify (group into smaller clusters) lipids necessary for lipase digestion

Secretin

stimulates bile secretions from liver

Cholecystokinin (CCK) (from the duodenum)

stimulates gallbladder contractions to release bile into the duodenum

Emulsification

combining two liquids that don't normally mix

causes fat droplets to disperse in water to expose more of the fat to lipase

When bile emulsifies fat

Functions of the Liver

1.) Bile production

2.) storage of nutrients

3.Processing of nutrients

4. Detoxification

5. Synthesis of new molecules

Pancreas exocrine function

Acinar cells (acini):

produce pancreatic digestive juices, which move through ducts to the small intestines

Endocrine function composed of

• Alpha cells

• Beta cells

• Delta cells

Alpha cells

secrete glucagon

Beta cells

secrete insulin

Delta cells

secrete somatostatin, which inhibits insulin/glucagon secretion

Na+, K+, HCO3−, water

Aqueous & enzymatic Pancreatic juice

Trypsin, chymotrypsin, and carboxypeptidase

Digest proteins.

Released in inactive forms in order to protect organs and glands

Pancreatic alpha-amylase

continues digestion of starch

Pancreatic lipase

continues digestion of lipids

Deoxyribonucleases & ribonucleases

digest DNA and ribonucleic acid, respectively.

Parasympathetic stimulation (vagus nerve)

Causes release of enzyme-rich pancreatic juice

Secretin (from duodenum)

causes release of aqueous pancreatic juice rich in bicarbonate

Cholecystokinin (from duodenum)

causes release of enzyme-rich pancreatic juice.

Duodenum

"mixing bowl", receives chyme from stomach and digestive secretions from liver/pancreas.

Jejunum

major site of nutrient absorption

Major & minor duodenal papillae

openings to ducts from the liver and/or pancreas

Circular folds of duodenum

folds of mucosa & submucosa which run perpendicular to the long axis of GI tract

Villi of duodenum

fingerlike projections of the mucosa that contain blood capillaries and lacteals

Lacteals of duodenum

transport chylomicrons that are too large to enter blood capillaries

Microvilli of duodenum

cytoplasmic extensions of absorptive cells; form the brush border, which produces additional enzymes

Small Intestine

Nutrients Are Absorbed in the

fingerlike projections called villi

Small intestine mucosa contains

have microvilli (gives the villi a fuzzy "brush border"

Cells that cover the villi

complete digestion

Microvilli contain brush border enzymes that

Microvilli/villi

What increases the surface area of the small intestines for absorption of nutrients?

villi

Nutrients are absorbed into the

Lacteals are

The small lymphatic capillary inside villi

villus

Monosaccharides & amino acids enter the blood capillaries of a

a lacteal

Glycerol & fatty acids form lipoprotein droplets called chylomicrons enter through

Depending upon the nutrient, absorption in small intestine occurs by

1.) Simple diffusion

2.) Facilitated diffusion

3.) Active transport

Monosaccharides, amino acids, & short-chain

What fatty acids are transported directly to liver by hepatic portal vein

lacteal and returned to the bloodstream via lymphatic system.

Long chain fatty acids are transported to a

Cell types in epithelium of small intestine

1.) Absorptive cells

2.) Goblet cells

3.) Granular cells (Paneth cells)

4.) Endocrine cells

Absorptive cells

produce digestive enzymes (disaccharidases (maltase, lactase, sucrase) and peptidases) & absorb digested food

Goblet cells

produce protective mucus

Granular cells (Paneth cells)

help protect from bacteria

Endocrine cells

produce regulatory hormones:

Gastrin

Gastric inhibitory peptide (GIP)

Secretin

Cholecystokinin (CCK)

Vasoactive intestinal peptide(VIP)

Mucus

Protects against digestive enzymes and stomach acids

Digestive (brush border) enzymes

Bound to the membranes of the absorptive (brush border)cells

Disaccharidases (maltase, sucrase, lactase)

Break down disaccharides to monosaccharides

Peptidases (enteropeptidase)

Hydrolyze peptide bonds

Lactase

the brush border enzyme that digests lactose

normal (lactose intolerance)

Not producing high levels of lactase in adulthood is

mutations that allow for sustained production of lactase into adulthood

Adults still producing high levels of lactase in adult hood is due to

Characteristics of Lactose Intolerance

diarrhea, gas, bloating, and abdominal cramps after ingesting milk and other dairy products

Intestinal glands

invaginations of the mucosa where epithelial cells are produced at the bases of villi

Absorptive & goblet cells

They migrate and cover the villi surface, and are eventually shed from the tip. Stem cells at bases replace shed cells

Paneth & endocrine cells

remain at the bottom of the intestinal gland

Jejunum & Ileum experience

Gradual decrease (↓) in diameter, thickness of intestinal wall, number of circular folds, and number of villi the farther away from the stomach.

Peyer patches

lymphatic nodules numerous in mucosa & submucosa that initiate immune responses against microorganisms.

Ileocecal junction

where ilium meets large intestine

gastroenteric reflex

stimulates motility and secretion along the entire small intestine

Ileocecal sphincter (valve)

remains slightly contracted until peristaltic waves reach it, causes it to relax and allow chyme to move into cecum

Gastroileal reflex

• Triggers opening of ileocecal valve

• Allows materials to pass from small intestine into large intestine

Vermiform appendix

Is a smaller sac attached to the cecum

• contain numerous lymph nodules that contribute to immune functions

4 parts of the colon

1. ascending colon

2. transverse colon

3. descending colon

4. sigmoid colon

Haustra

pouches (bulges) of the large intestine that allow expansion and elongation

Crypts

Mucosa in the colon has numerous straight tubular glands called

Crypts include 3 cell types

1.) Goblet cells

2.) Absorptive cells

3.) Granular cells (Paneth cells)

Rectum

Temporary storage of feces

Anal canal sphincters

-internal anal sphincter (smooth muscle involuntary)

- external anal sphincter (skeletal muscle voluntary)

Internal anal sphincter

(smooth muscle(involuntary) layer even thicker than the rectum)

External anal sphincter

(skeletal muscle(voluntary) at inferior end of the canal)

Hemorrhoids

Rectal vein enlargement or inflammation.

Treat with changes in diet or medications

Functions of the Large Intestine

1) Does not produce digestive enzymes.

2) Does not absorb nutrients except certain vitamins.

3) Absorbs vitamins produced by intestinal flora (bacteria)

4) Absorbs water from feces to prevent dehydration

5) Forms feces

6) Defecation

Movement in the Large Intestine

mass movements, local reflexes, defecation

Gastrocolic (local reflex)

initiated by distention (enlarged) in the stomach

Duodenocolic (local reflex)

initiated by distention (enlarged) in the duodenum

Defecation reflex

Swelling/enlargement of the rectal wall by feces distension

apical membrane

Side of epithelium facing lumen

basolateral membrane

Side of epithelium facing blood vessels

Carbohydrates

Polysaccharides, disaccharides, and monosaccharides

Secondary Active Transport

Form of active transport which does not use ATP as an energy source; rather, transport is coupled to ion diffusion down a concentration gradient established by primary active transport.

Lipids

Include triglycerides, phospholipids, steroids, fat-soluble vitamins

Lipases

digest lipid molecules; products include free fatty acids and monoglycerides.

Micelles

lipid droplets surrounded by bile salts

chylomicrons

Micelles absorbed by epithelial cells, lipid contents repackaged into

adipose tissue

Chylomicrons enter lacteals and eventually blood, travel to

lipoprotein

A group of soluble proteins that combine with and transport fat or other lipids in the blood plasma.