a&e chap16 medic12

Digestive Tract

1) oral cavity
2) pharynx
3) esophagus
4) stomach
5) small intestine
6) large intestine
7) rectum
8) anus

In some areas portions of the digestive tract are suspended. By what means are they suspended?

Mesenteries

What are mesenteries composed of?

Double sheets of peritoneal membrane.

Muscularis externa propels materials through the digestive tract by what means?

the contractions of peristalsis

segmentation movements

in areas of the small intestine churn digestive material

Stomach Major Functions

1) temporary storage of ingested food
2) mechanical breakdown of food
3) breakage of chemical bonds by acids & enzymes
4) production of intrinsic factor

Chyme

forms in the stomach as gastric & salivary secretions are mixed with food

Regions of the Stomach

1) cardia
2) fundus
3) body
4) pylorus

pyloric sphincter

guards the exit from the stomach

rugae

numerous ridges & folds found in the stomach lining when in a relaxed state

what do parietal cells, located within the gastric gland, secrete?

intrinsic factor & hydrochloric acid

what do chief cells secrete?

pepsinogen

what do acids in the gastric lumen convert pepsinogen into?

pepsin (enzyme)

what do gastric gland endocrine cells secrete?

gastrin (hormone)

gastric secretion phases include

1) cephalic phase, prepares the stomach to receive ingested material
2) gastric phase, begins w/ the arrival of food in the stomach
3) intestinal phase, controls the rate of gastric emptying

small intestine includes

1) duodenum
2) jejunum
3) ileum

ileocecal valve

is a sphincter & marks the junction between the small & large intestines

what are the transverse folds found in the intestinal mucosa?

plicae

what are the small projections found in the intestinal mucosa?

intestinal villi

what do plicae & intestinal villi do?

these structures increase the surface area for absorption

lacteal

lymphatic capillary found in each villus

why do smooth muscle cells in the muscularis externa of the small intestine contract periodically, without stimulation?

to produce brief localized peristaltic contractions that slowly move materials along the tract.

peristaltic activities, greater than those of the muscularis externa, are coordinated by?

gastroenteric & the gastroileal reflexes

what do intestinal glands secrete?

1) intestinal juice
2) mucus
3) hormones

what does intestinal juice do?

1) moistens the chyme
2) helps buffer acids
3) dissolves digestive enzymes & the products of digestion

intestinal hormones include

1) gastrin
2) secretin
3) cholecystokinin (CCK)
4) gastric inhibitory peptide (GIP)

where do most of the digestive & absorptive functions occur?

in the small intestine

digestive enzymes & buffers are produced by what organs?

1) pancreas
2) liver
3) gallbladder

pancreatic duct

penetrates the wall of the duodenum, where it delivers the secretions of the pancreas.

what functions does the pancreas have?

1) endocrine (secretes insulin & glucagoninto the blood)
2) exocrine (secretes water, ions, & digestive enzymes into the small intestines)

what enzymes does the pancreas secrete?

1) carbohydrases
2) lipases
3) nucleases
4) proteases

pancreatic juice

watery substance produced by the pancreatic exocrine cells in response to instructions from the duodenum.

what hormones are released when chyme arrives in the small intestine?

secretin & CCK

release of secretin triggers what for the pancreas to produce?

a fluid that contains buffers (primarily sodium bicarbonate) that help bring the pH of the chyme under control.

CCK stimulates the pancreas to produce & secrete what?

1) pancreatic amylase
2) pancreatic lipase
3) nucleases
4) several proteolytic enzymes (trypsin, chymotrypsin, & carboxypeptidase)

liver

- largest visceral organ in the body
- performs over 200 known functions

liver made up of...

4 unequally sized lobes
1) left
2) right
3) caudate
4) quadrate

liver lobule

organ's basic functional unit

how is blood supplied to the liver lobules?

by branches of the hepatic artery & hepatic portal vein.

list some specific major functions of the liver?

1) metabolic regulation
2) hematological regulation
3) production of bile

gallbladder

stores & concentrates bile for release into the duodenum

what permits bile to enter the duodenum?

relaxation of the hepatopncreatic sphincter by CCK

main functions of the large intestines

1) reabsorb H2O & compact feces
2) absorb vitamins made by bacteria
3) store fecal material prior to defication

parts of the large intestine

1) cecum
2) colon
3) rectum

cecum

collects & stores material from the ileum & begins the process of compaction

colon

1) larger diameter & thinner wall than the small intestine
2) bears haustra (pouches) & taeniae coli (longitudinal bands of muscle)

rectum

terminates in the anal canal, wh/ leads to the anus

The sodium potassium exchange pump maintains a gradient of sodium & postassium ions across the cell membrane. What is more concentrated inside the cell?

Potasium

The sodium potassium exchange pump maintains a gradient of sodium & postassium ions across the cell membrane. What is more concentrated outside the cell?

sodium

For each ATP molecule consumed by a Sodium-Potassium exchange pump, what & how many molecules are pumped out(ejected) & what & how many molecules are pumped in(reclaimed)?

3 sodium ions ejected & 2 potassium ions reclaimed