unit 1: digestive

organs of alimentary canal

Mouth, pharynx, esophagus, stomach, small intestine, large intestine (MELPSS)

Accessory organs

teeth, tongue, salivary glands, liver, gallbladder, pancreas

difference b/w alimentary organs and accessory organs

food doesn’t ACTUALLY enter the accessory organs, since they assist in the process of digestion only

mechanical digestions

breaking up food by physical means

chemical digestion

using chemicals to breakdown food

four layers of alimentary canal

serosa, muscularis, submucosa, mucosa

what is peristalsis?

rhythmic contractions of smooth muscle of an organ resulting in food being pushed along

where does peristalsis occur?

all throughout the alimentary canal

1st part of path

mouth (aka oral cavity)

mouth

beginning of alim, canal

function of mouth

receives food, breaks it down, moistens it

teeth

break off food,

What’s the word for teeth chewing food?

mastication

two structures responsible for ensuring food goes in the proper direction when swallowed

epiglottis and uvula

tongue

mixes food with saliva, contains papillae (tiny bumps)

what do the papilllae help with?

gripping food (increase friction) to move it toward the pharynx

A bolus is

food shaped into a moist/saliva round structure

Hard palate

roof of mouth (mostly of maxillary bone, small amount is palatine)

soft palate

posterior to hard palate, has uvula attached to it

____ and ___ move up and back during ____ to partially block opening into nasal cavity

soft palate, uvula, swallowing

role of tonsils

contain lymphatic tissue, WBC to fight infection

3 sets of tonsils

palatine, pharyngeal, lingual

palatine tonsils

may interfere w/ food or drink

pharyngeal tonsils aka

adenoids

pharyngeal tonsils

interfere w/breathing

lingual tonsisl

posterior region of tongue

salivary galnds

release saliva through small ducts to bind and moisten foods

saliva contents

water, mucous, salivary amylase

salivary amylase is the enzyme that begins chemical digestion of ________

carbohydrates

lysozyme

antibacterial enzyme, protects teeth (against cavities)

locations of salivary galnds

sublingual, parotid, submandibular

These two organs don’t undergo digestion or absorption

pharynx and esophagus

pharynx aka throat

transports food to esophagus, 3 regions

esophagus

transports food to the stomach

food is passed through an opening in the diaphragm (_______ _______) to reach the stomach

esophageal hiatus

hiatal hernia (esophagus/stomach)

stomach pushes up thru diaphragm into chest cavity thru hiatus

A hiatal hernia can encourage ____ ___ to enter the esophagus which is known as

stomach acid; Gastro esophageal Reflux Disease (GERD)/ Heartburn

sphincters

circular rings of smooth/skeletal muscle normally constricted (relaxed to allow passage), 6 total

1st spincter: Lower esophageal spincter

at junction of esophagus and stomach, near the heart

lower esophageal sphincter aka

cardiac sphincter

four regions of stomach (right to left)

fundic, body, pyloric, cardiac

rugae

thick folds on inner wall, pouch-like, holds 1.5 L

stomach has three layers circular, longitudinal and oblique for extra _____ ____

churning action

gastric pits

indentations on inner stomach wall

each cell of the three types of cells on the stomach wall contributes to ______ ____

gastric juice

The 3 types of cells of the stomach wall

mucous, chief, parietal

mucous cell

contributes mucous, alkaline secretion

cheif cells

contributes pepsinogen (important for dietary protein digestion)

mucous cells

mucous, prevents stomach from digesting itself (acidic environment)

parietal cells

secretes intrinsic factor: used for absorption of Vit. B12, which is needed for hematopoiesis, and HCl solution

hormone from stomach that stimulates release of gastric juice and stomach peristalsis

gastrin

semifluid paste when food mixes up in stomach plus gastric juices

chyme

very little _________ from stomach into bloodstream (H2O, medications—> exceptions, ex. Advil quickly blocks pian signals)

absorption

chyme enters the ______ (first segment of the small intestine) through the ______ ________.

duodenum, pyloric spincter

______ of chyme must be neutralized.

acidity

secretin

stimulates pancreas to release pancreatic juice into duodenum

secretin is rich in _____________ ____.

bicarbonate ions

contents of pancreatic juice

pancreatic amylase (breakdown of carbs) and lipase (breakdown of lipids), proteases (breakdown of proteins)

3 inactive precursors leading to trypsin, chyptrypsin, carboxypeptidase which furhter break down proteins in the small intestine

trypsinogen, chymotrysinogen, carboxypeptidogen

what enzyme activates the protein-digesting enzymes form the pancreas that are in inactive form?

enterokinase

Cholecystokinin (CCK) hormone of small intestine

stimulates release of bile from the gallbladder

must pass thru the Hepatopancreatic spincter to enter the _______ __________.

bile and pancreatic juice; small intestine

liver

largest visceral organ

functions of liver

storage of glucose (as stored form glycogen), storage of vitamins (fat soluble vitamins), metabolizing proteins, fats, cholesterol, detoxification (alcohol), formation and secretion of bile (into gallbladder)

bile

water w/ cholesterol molecules, very diluted (cholesterol-based solution, used for emulsification of fats

gallbladder

small thin sack used for storing, concentrating bile

emulsification

breaking large fat molecules into smaller ones, increases surface area, allows enzymes to work efficiently, absorbs fluid from bile, increasing the concertation of fluid

Too much water is absorbed, cholesterol can precipitate turning into a solid forming a

gallstone

chyme—> smal intestine—> cck—>bile—>emulsification—> final secretion of enzymes to breakdown food—>reabsorb water—> elimination

specifics of pathway in Dig. tract

small intestine

6 m (20 feet long), extends from pyloric sphincter (end of stomach) to ileocecal sphincter (beginning of stomach, cecum)

3 segments of small intestine

duodenum, jejunum, ileum DJI

which segment does the most enzymatic activity and absorb the most nutrients?

duodenum d/t huge surface area

enzymes secretes to finish breakdown of food

intestinal enzymes

intestinal lipase

digestion of fatty acids

amino peptidase

splits amino acids

sucrose, maltase, lactose

act up disaccharides (hydrolysis)

nucleases

act upon nucleic acids

plicae circularis, villi

mucosal surface very irregular, with finger-like projections

Both plicae circularis and villi

increase surface area

villi contain capillaries for absorption of ________ and _______

glucose and amino acids

villi contains lacteals for absorption of ______ ______

fatty acids

infection/irritation in the small intestine will increase peristalsis and move material quickly through the small and large intestine

peristaltic rush aka diarrhea

ileocecal valve (sphincter)

regulates movement of material into large intestine

large intestine aka

colon

large intestine

reabsorbs water, forms solid waste

cecum

first segment of colon, has vermiform appendix attached

cecum—> ascending colon—>transverse colon—> descending colon—> sigmoid colon—> rectum—>anal canal—> internal and external anal sphincter

large intestine path

anal canal

internal and external sphincter muscles

contracted until pressure from solid waste stimulates it to relax

internal sphincter

external anal spincter

voluntary, skeletal

can be contracted to keep solid waste in until appropriate to allow it to relax

external spincter

final step after waste passes thru large intestine spincters

defecation, elimination