Digestion

Basic Digestive Functions and Processes

• ingestion

• secretion

• propulsion

• mechanical digestion

• chemical digestion

• absorption

• excretion

ingestion

getting things into the digestive system

secretion

mucus enzymes acid and hormones to aid other digestive processes

propulsion

rhythmic contractions of smooth muscle of alimentary canal (peristalsis)

mechanical digestion

digestive organs physically break food down into smaller pieces

chemical digestion

break organs physically break food down into smaller pieces

chemical digestion

break chemical bonds within food particles until only small molecules remain

absorption

move nutrient from outside the body to inside the body

excretion

pooping

between two peritoneal layers is

peritoneal cavity contains serous fluid

organs located entirely within peritoneal cavity are

intraperitoneal

other organs are

retroperitoneal

visceral peritoneum folds over on itself to form

mesenteries

greater omentum is

unique among mesenteries in that it consists of four layers of folded visceral peritoneum, extends from base of stomach down into pelvis

lesser omentum

smaller mesentary that extends from medial surface of stomach to liver

Digestive system main functions is

take nutrients from the external environment and use it for the internal environment and excrete waste.

What is peristatlsis

muscle reflex of the esophagus (smooth muscle) in order for it to go down into the system

Two mesenteries are

greater omentum

lesser omentum

Mesenteries holds and supplies

small intestine

celiac trunk

supplies the stomach, accessory organs, and spleen

superior mesenteric

supplies the smal intestine and proximal 2/3 of the colon

inferior mesenteric

supplies the distal 1/3 of colon, drain into hepatic portal vein to liver for processing

(regulation of motility by the nervous and endocrine systems) movement of alimentary canal is

• swallow

• churn

• peristalsis

• defecation

skeletal muscle (regulation of motility by the nervous and endocrine systems)

• mouth

• pharynx

• superior 1/3 of esophagus

• anus

• voluntary

smooth muscle (regulation of motility by the nervous and endocrine systems)

everything else

enteric nervous system (regulation of motility by the nervous and endocrine systems)

• ENS is self-contained branch of autonomic nervous system

• extends from esophagus to anus

• Functions stimulated by ENS are short reflexes

• reflex pathways are confined to local neurons

oral cavity

• ingestion

• secretion

• chemical and mechanical digestion - saliva

• propulsion

Enteric means

small intestine

serous cells (acinar cells)

• secrete water-based fluid with amylase to break down carbohydrates

• IgA

• bicarbonate - accepts acidic

mucous cells (acinar cells)

secrete mucus keeps things slimy and moist

local potenials are

influence by amount of nerves or the speed by the target nerve

facial nerve

innervate submandibular and sublingual glands

glossopharyngeal nerve

innervate parotid glands (salivary glands), also monitor gases in the blood

palatine tonsils and lingual tonsils

• tonsils perform defensive functions

  • protect remainder of alimentary canal from any pathogens that enter body via oral and nasal cavities

epithelium of the mucosa is

simple columnar epithelium

superior third of esophagus is

skeletal muscle

middle third of esophagus

mixture of skeletal and smooth muscle

inferior third of esophagus is

• smooth muscle

• upper esophageal sphincter - controls passage of bolus into esophagus

• gastroesophageal sphincter prevents contents of stomach from re-entering esophagus

primary functions of esophagus are

propulsion and small amount of secretion of mostly mucus

Esophagus pierces diaphragm and passes through

esophageal hiatus to empty into the stomach

Stomach has a third layer called

oblique layer

three muscle layers of the stomach are

• extra oblique layer

  • for mechanical digestion

chemical digestion

gastric glands - at base of gastric pits

significant protein digestion

mucous neck cells

secrete acidic mucus

• prevents neutralization of acid produced by parietal cells

parietal cells

secrete hydrocholoric acid

• activates pepsinogen

• destroys many disease-causing organisms

  • intrinsic facor required for intestinal absorption of vitamin b12

chief cells

secrete pepsinogen

• when pepsinogen encounters acidic pH it becomes active enzyme pepsin (activated by hydrochloric acid)

G cells

secrete gastrin

stimulate secretions from other cells (manager of the operation)

most of the structural protein are

collagen

Functional protein

globular proteins and are in form of enzymes (takes up 99%)

functional form of lipids

cholesterol

structural form of lipids

phospholipids

triglycerides are ___ and are stored in

storage form of lipids and stored in fat cells

enzymes are

proteins

enzymes use ____ in order to function

water (hydrolysis)

enterocytes are what kind of cells

simple columnar epithelium

polymers of carbohydrates (plants)

cellulose

Starch break down into

dissacharide

Glucose and galactose needs what element in order to function

sodium

Fructose uses what kind of diffusion

facilitated diffusion

Glycogen is stored in the

liver

Pepsinogen requires ph of about ___ to become pepsin

2 ph

pepsin reaction catalyze only about ______ of proteins in ingested food

10-15%

Trypsin is in the _____ and one of the main function of breaking down protein other than pepsin

intestine

inactive precursors protect pancreas from

autodigestion

Majority of lipids (90%) are taken in as

triglycerides

mechanical digeestion

mastication in mouth, churning in stomach, and segmentation in small intestine

• bile salts in small intestine are amphiphilic with polar and nonpolar parts

what kind of transport do lipids need to have

it doesn’t because of hydrophilic material

nucleic acids in food begin chemical digestion in small intestine with help of pancreatic enzymes called

nucleases

Pepsin vs. trypsin

pepsin in the stomach, trypsin in the pancreas

most electrolytes are absorbed in

small and large intestine

vitamins

chemicals that generally provided by diet, host of metabolic reactions

two types of vitamins

water soluble vitamins - polar molecules

fat-soluble vitamins - lipid-based and mostly nonpolar

water-soluble vitamins are

b12 and c

fat soluble vitamins

K,A,D,E