Chapter 25 final

Ingestion, Digestion, Absorption, compaction, defacation

digestive system functions

mechanical digestion

chewing and churning of the stomach

chemical digestion

breaking macromolecules into monomers due to enzyme released in the saliva, stomach, bile, pancreas and small intestine

digestive tract

a muscular tube running from mouth to anus, about 16 feet long

mouth, pharynx, esophagus, stomach, small intestine, large intestine

order of the digestive tract

cross section of the digestive tract

mucosa epithelium, sub mucousa, muscularis external, serosa

mucosa

the surface or lining epithelium, simple colomunar where it absorbs, has MALT on laminate propria

stratified squamous

innermost laer of the mucosa, in the mouth pharynx, esophagus, and anus to handle abrasion

muscularis mucosa

outermost layer of the mucosa, is a leyr of smooth muscle

submucosa

connective tissue with blood vessels, lymphatics and nerve plexuses, the supportive layer

muscularis externa

thick layer of muscle in the wall of the gastrointestinal (GI) tract that lies just outside the submucosa

inner layer of muscularis externa

circular, good for sphincter formation

sphincter formation

specialized thickening of the circular muscle layer of the muscularis externa, which creates a ring-like muscle that can tightly close a passage or opening in the body.

outer layer

longitudinal, good for peristalsis

serosa

thin layer of areolar tissue, has simple squamous mesothelium in the outermost layer

eneteric nervous system

network of neurons embedded in the walls of the gastrointestinal tract, the enteric nervous system,regulates digestive motility, secretion and blood flow, motor input is primarily autonomic, has two layers: submucosal plexs, myenteric plexus

submucosal plexus

in the submucosa, controls secretions and has some sensory nerves

myenteric plexus 

between the 2 layers of the muscularis external, controls peristalsis

mesentery

double layer of peritoneum that anchors portions of the intestines to the posterior abdominal wall while still allowing them some mobility, this is where blood vessels, lymphatics and nerves run

abdominopelvic cavity

the space in the abdomen and pelvis that houses most digestive organs.

parietal peritoneum

serous membrane that lines the wall of the abdominal cavity

posterior mesentery

when the parietal peritoneum leaves the back of the cavity as a 2-layered membrane, translucent and extends to the digestive tract

serosa

when the posterior mesentery reachs an organ it splits around it and forms this

omenta

extensions of the mesentery that from anterior connections

lesser omentum

short mesentery running from the liver to the right side of the stomach

greater omentum

fatty mesentery hanging off the left side of the stomach

mesocolon

the mesentery to the colon

intraperitoneal

an organ has to be completely surrounded by this in order to be considered this, inside the peritoneal cavity and not fixed

retroperitoneal

lies behind the peritoneum and is only covered by the perotnieum on its anterior surface

myenteric reflexes

feedback causes muscularis externa contractions with resulting peristalsis, do not involve the brian or the spinal cord

vasovagal reflexes

These reflexes connect the digestive tract to the central nervous system.They involve afferent (sensory) signals traveling to the brainstem and efferent (motor) signals returning via the vagus nerve.

buccal cavity

also called the mouth, starch digestion begins here, lined by stratified squamous epithelium, keratinised on parts like the hard palate most subject to abrasion

upper and lower labial frenulum

attach the inside of the lip to the gum, located in the midline between the incisors

vermillion

pink portion of the lips

labial mucosa

the inner portion of the lips facing the teeth

vermillion border

where the lips meet the skin, must be carefully aligned if sutruing of an injury is required

labial mucosa

inner portion of the lips facing the teeth

tongue

non-keratinized stratified squamous epithelium, anterior 2/3 of it is in the oral cavity and the posterior 1/3 is in the oropharynx

lingual frenulum

attaches the body of the tongue to the floor of the mouth

lingual glands

located amid the muscles of the tongue, salivary glands

intrinsic m

used for fine movement in the tongue (talking)

extrinsic muscle

used for stronger movement (chewing)

lingual tonsils

tonsils that are located in the throat

palate

separates the oral and nasal cavities

bony hard palate

anterior portion of the palate

soft palate

posterior portion of the palate, muscular and the uvula hangs on this

palatoglossal arche

anterior fold; runs from the soft palate to the side of the tongue.

palatophrangyeal arch

the posterior fold; runs from the soft palate to the pharynx (throat).

dentition

collective term for teeth

incisors

cut food

premolars and molars

grind

gomphosis

the tooth joint

periodontal ligament

ligament thatlines the socket and its collagen fibers penetrate the tooth and bone both, anchor the tooth

gingiva

what the gum is called

gingival sulcus

a shallow grove betewen the tooth and the gingivia, can collect plaque and bacteria leading to gingivitis

enamel

covers the crown, devoid of cells and cannot regenn

cementum

covers the root

pulp cavity and root canal

deep to the dentin, where blood vessels and nerves are located

occlusion

the meeting of the upper and lower teeth

deciduous teeth

“baby” teeth which erupt from 6-30 months

mastication

chewing

masseter

elevates the mandible and closes the jaw

temporalis

depresses the mandible

saliva

moistens, inhibits bacterial growth,dissolves food, initiates starch and lipid digestion, lubricates with mucus

mucus, electrolytes, lysosomes, IgA, amylase, lipase

saliva contains

intrinsic/minor salivary glands

dispersed among the other oral tissues: tongue, lips palate, cheeks, and give off secretions chronically to kepe

extrinsic/major salivary glands

larger and more discreet

parotid glands

where the mumps virus primarliy infects anterior and inferior to the ear

sumandibular glands

under the mandible

sublingual glands

under the tongue

salivation

the extrinsic salivary glands produce 1 L a day of saliva in response to food, controlled by parasympthetic input from salviatory nuclei in the branstem: can inhibit salivation and cause a dry mouth

esophagus

straight msucular tube that passes through the diaphragm to intersect with the stomach

esophageal sphincter

located at this intersection, prevents the reflux of food back into the esophagus

heartburn

becuase the epithelium of the esophagus is stratified squamous and not desigined to withstand gastric acid there are these symptoms if reflux occurs

deglutition

physiologic term for swallowing

medulla

coordinates the swallowing center

pharyngeal phase

involuntary , the layrnx comes up to meet the epiglottis while pharyngeal constrictors contract in a carefully coordinated order

esophageal phase

involuntary and due to presistalis with both brainstem and myenteric plexus reflexes occurring

stomach

muscular sac just below the diaphragm, primary function is food storage, it churns to mechanically break down food, it liquifes food and begins digestion of proetins and fats

chyme

end product of gastric action

cardiac part

the uppermost 3 cm of the stomach

fundus

the dome superior to the esophageal attachment

body

main portion of the stomach

pyloric part

most inferior portion of the stomach which terminatesinto the pylorus

plyorus

the narrow entrance into the duodenum where a plyoric sphincter is found

vagus nerve

parasympathetic innervation is supplied by this nerve in the stomach

celiac ganglion

sympathetic input to the stomach comes from this

celiac trunk

blood is supplie to the stomach by this

portal vein

blood returns via the portal circulation through the liver

gastric glands

located indepressions called gastric pits, have many different types of cells

mucus cells

secrete mucus

regenerative cells

supply replacement cells for normal mucosal turnover

parietal cells

secrete HCL,intrinsic factor and ghrelin (appetite stimulate)

chief cells

secrete digestive enzymes

eneteroendocrine cells

secrete hormones and paracrine

.8

gastric juice pH

carbonic anyhdrase

parietal cells make this enzyme which makes H+ and Cl+ which combines in the lumen and make HCl

Hydrochloric acid

activates enzymes, provides food breakdown, converts Fe(3+) into Fe(2+) which increases iron absorption

pepsin

comes from chief cells for protein digestion

lipase

comes from chief cells for fat digestion