Digestive System: Small Intestine to Rectum

small intestine

convoluted tube extending from pyloric sphincter to the ileocecal valve where it joins large

small intestines

these are the three subdivision of this:

• duodenum

• jejunum

• ileum

deudenum

subdivision of small intestine

• shortest intestinal region

  • bile duct and main pancreatic duct here

hepatopancreatic ampulla

the bile duct and main pancreatic duct combine in duodenum to form this

jejunum

middle region of small intestine

• intraperitoneal

• mesentery suspended from posterior wall

ileum

subdivision of small intestine that joins large intestine at ___ valve

absorption

modifications of SI for ______

• length

• circular folds

• villi

• microvilli

circular folds

deep, permanent folds in small intestines that force chyme to spiral for nutrient absorption

villi

are finger-like projections lining the small intestine's inner surface

• lacteal: lymph capillary

microvilli

Tiny, microscopic projections on the surface of cells, particularly those lining the villi

intestinal juice

control of this:

• 1 to 2L/day

• stimulus: distension or irritation of mucosa by acidic chyme

intestinal juice

composition of this:

• mainly water

• slightly alkaline

• enzyme poor

liver

• largest gland in body

• under diaphragm on right

• mesentery

• 4 lobes

liver lobes

• right

• left

• caudate

• quadrate

liver

digestive function: produce bile

emulsifier

breaks down fat into tiny particles so its easier to digest in liver

common bile duct

bile leaves liver through several bile ducts which fuse to form __________

small intestine

common bile duct drains here

liver lobules

liver is composed of small units called ___ ___ composed of hepatocytes (liver cells)

hepatocytes

liver cells that fan around a central vein

functional unit

smallest unit of an organ that can carry out its function

• ex. liver lobules

1. produce bile

2. produce blood born nutrients

3. store fat and vitamin

4. filter waste and nutrients

1-4 roles of heptocytes

portal triad

in corner of lobule

• consists of hepatic arteriole, a hepatic venule, and bile duct

sinusoids

in between walls of hepatocytes

• large, leaky capillaries - macrophages in these capillaries that remove debris from blood

hepatitis

DEF: inflammation of liver

CAUSE: viral infection

• 6 strains that can cause

cirrhosis

progressive, chronic inflammation of the liver

• caused by: chronic alcoholism or severe hepatitis

bile

yellow, green alkaline solution that contains bile salts, bile pigments such as bilirubin, cholesterol, fats, phospholipids, and electrolytes

• 500-1000 ml/day

gallbladder

thin-walled, green muscular sac located in a ventral fossa of the liver

gallbladder

stores bile that is not immediately needed for digestion and concentrates it

cystic duct

bile expelled here before traveling to bile duct

gallstones

cholesterol crystalization

CAUSE: too much cholesterol and/or too few bile salts

SYMPTOMS: intense pain in right thoracic region

gallstones

RESULTS IN: obstruction of bile flow from gallbladder

TREATMENT: dissolve crystal with medicine, ultrasound vibrations, or removing gallbladder

pancreas

gland that extends across abdomen from its tail to its head (encircled by duodenum)

• retroperitoneal

pancreas

function: produce enzymes that breakdown foodstuffs and delivers enzyme to duodenum through MAIN PANCREATIC DUCT

• exocrine product call pancreatic juice

zymogen granules

the pancreas contains these digestive enzymes

acini

the pancreas contains _____, or clusters of secretory cells that surround ducts, full of rough endoplasmic reticulum

water, enzymes, electrolytes

Primary composition of pancreatic juice

pancreatic juices

the high pH of this helps neutralize the acidity of chyme and improves environment for enzymes to work

bile salts

____ ___ are the major stimulus for bile secretion

gallbladder

if there is no digestion, released bile is stored here until needed

• hepatopancreatic sphincter closed

CCK and secretin

intestinal hormone released when acidic chyme enters duodenum

CCK and secretin

stimulates release of pancreatic juices and relaxes hepatopancreatic ampulla sphinster so that exocrine substances can enter duodenum

chyme is hypertonic

reason why chyme delivery is slow to SI

• a large amount of chyme entering would cause a fluid shift

pH must be adjusted

reason why chyme is delivered slow to SI

• small intestine cannot handle acid like stomach

segmentation

food moved forward and backward by alternating contractions and relaxations of smooth muscle

• pacemakers control rhythm

• most common movement in SI

peristalsis

this begins after most nutrients have been digested in small intestine

motilin

hormone that stimulates peristalsis

• duodenal mucosa releases

Migrating Mobility Complex

sweeping the last remnants of the meal to the large intestine from small

• prevents bacteria overgrowth

large intestine

digestive function is to absorb remaining water from indigestible food residue, store temporarily and eliminate feces

• from ileocecal valve to anus

teniae coli

feature of large intestine

• longitudinal muscle with 3 layers that cause intestine to pucker

haustra

large sacks formed in large intestine from teniae coli

epiploic appendages

small, fat-filled pouches of visceral peritoneum that hang from large intestine with an unknown purpose

• unique feature

cecum

sac-like region below ileocecal canal

• 1st part of large intestine

reformed appendix

lymphoid tissue called MALT found in large intestine

transverse, sigmoid

two colons that are intraperiotoneal

appendicitis

acute inflammation of appendix

CAUSE: blockage (often by feces) that traps infectious bacteria in its lumen

appendicitis

RESULT IN: swelling of appendix which blocks of venous drainage, may lead to ichema and necrosis

SYMPTOMS: pain in umbilical region; loss of appetite, nausea, vomiting

circular folds, vili, secretory cells of enzymes

what large intenstinal microanatomy lacks compared to small

what LI has and SI lacks

THICKER mucosa

DEEPER crypts

LARGE NUMBER of goblet cells

water, electrolytes

the large intestine absorbs ____ and ____, but not nutrients

large intestine

function is really to propel fecal material towards anus and eliminate it

defecation

mass movements force feces into rectum

• muscles of rectum contract to expel feces

haustral contractions

slow segmenting contractions

• mainly in TRANSVERSE and DESCENDING colon

haustral contractions

hastrum fills with residue and distension stimulates contraction to propel forward

mass movements

long, powerful, slow-moving contractile waves that move contents toward rectum

diarrhea

watery stools

CAUSE: ANY CONDITION THAT RUSHED FOOD RESIDUE THROUGH LARGE INTESTINE BEFORE WATER CAN BE ABSORBED

• bacteria, jostling of digestive viscera

constipation

stool that has remained in colon too long and becomes difficult to pass

• lack of fiber, improper bowel habits, lack of exercise, emotional upset, laxative abuse