GI Tract: mouth, stomach, intestine, etc.

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copied from another user and from my textbook

small intestine

Approx. 2.5cm wide + 7m long. Arranged in series of orderly loops. Divided into 3 parts.

duodenum

first 25-30cm, most chemical digestion takes place here.

jejunum

3m long, absorption into the circulatory and lymph system

ilium

3m long, end of small intestine

muscle layers

circular and longitudinal, move material by peristalsis

mucosa

folds, projecting from folds are small finger like villi. increase surface area

liver

performs more than 500 functions, production of bile, stores glycogen etc.

gallbladder

Stores bile until needed

pancreas

produces sodium bicarbonate, and many digestive enzymes.

large intestine

shorter than small intestine, but twice the diameter. main use is reabsorption of water and production of vitamin B and K. has three sections

ascending colon

rises up on the right of the abdomen

transverse colon

crosses middle of abdomen

descending colon

goes down left side of abdomen, terminates at rectum.

mouth

Mechanical and chemical digestion begins here. Physical breakdown of food by teeth

gastrointestinal tract

a one-way digestive tract that makes possible the seperation of digested and undigested food. (also known as GI tract)

tongue

forms a bolus (ball) out of the chewed food + pushes it to the back of the mouth into the pharynx

esophagus

inner layer called the mucosa, allows for smooth movement of food. Bolus activates stretch receptors which in turn activate smooth muscles that start peristalsis

peristalsis

major means of propulsion (adjacent segments of the alimentary canal relax and contract)

stomach

J-shaped - mostly involved in digestion but small amount of absorption

mucosa

The first main layer. This consists of an epithelium, the lamina propria composed of loose connective tissue and which has gastric glands in it underneath, and a thin layer of smooth muscle called the muscularis mucosae.

mucous

protects stomach lining

enzymes

protein substances that speed up chemical reactions.

pepsin

enzyme that breaks down proteins

mesentary

a double layer of peritoneum; holds organs in place, sites of fat storage, provides a route for circulatory vessels and nerves

cardiac sphinctor

Regulates movement of food into stomach and helps to prevent it from going back into the esophagus.

pyloric sphinctor

located between stomach and small intestine, controls the movement of partially, digested food.

ingestion

the process of taking food into the body through the mouth (as by eating)

digestion

The breakdown of complex organic molecules into smaller components by physical and chemical means

absorption

the taking up of digested molecules into the cells of the digestive tract

Defecation

the removal of waste (indigestible substances as feces) from the body

sigmoid colon

the part of the large intestine between the descending colon and the rectum

bile

a digestive chemical that is produced in the liver, stored in the gall bladder, and secreted into the small intestine

chyme

food in the stomach that is partly digested and mixed with stomach acids.

Where does chyme go?

Chyme goes on to the small intestine for further digestion.

alimentary canal

the passage through which food passes, including the mouth, esophagus, stomach, intestines, and anus.

submucosa

This layer lies over the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer. The Meissner's plexus is in this layer (blood and lymphatic vessels, nerve fibers)

muscularis externa

Over the submucosa, this area in the stomach differs from that of other GI organs in that it has three layers of smooth muscle instead of two.

serosa

This layer is over the muscularis externa, consisting of layers of connective tissue continuous with the peritoneum.

cecum

is a pouch, connecting the ileum with the ascending colon of the large intestine (it is separated from the ileum by the ileocecal valve) and is considered to be the beginning of the large intestine.

ileocecal valve

separates the ileum from the ascending colon of the large intestine

epiploic appendices

They are small pouches of the peritoneum filled with fat and situated along the colon and upper part of the rectum.

appendix (or vermiform appendix)

is a blind-ended tube connected to the cecum

teniae coli

are three separate longitudinal ribbons of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons. (teniae coli contracts length wise to produce the haustra, the bulges in the colon)

rectum

is the final straight portion of the large intestine and terminates in the anus.

Anus

(from Latin ānus meaning "ring", "circle") is the external opening of the rectum. (its closure is controlled by sphincter muscles)

Accessory digestive organs

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

Mechanical digestion

prepares food for chemical digestion
Chewing, churning food in stomach, segmentation

Segmentation

is rhythmic local constrictions of intestine and mixes food with digestive juices

Chemical digestion

complex molecules broken down to chemical components; in Mouth, Stomach and Small intestine

two layers of the muscularis externa

Circular muscularis—inner layer
Longitudinal muscularis—outer layer

Peritoneum

a serous membrane (2 types)

Visceral peritoneum

surrounds digestive organs

Parietal peritoneum

lines the body wall

Peritoneal cavity

a slit-like potential space

Lesser omentum

attaches liver to lesser curvature of stomach
(one of the two layers of the mesentary)

Greater omentum

a "fatty apron" of peritoneum, small intestine to posterior abdominal wall. (one of the two layers of the mesentary)

labial frenulum

Connects lips to gum

The palate

Forms the roof of the mouth
(2 areas: hard and soft)

Lingual frenulum

Secures tongue to floor of mouth

Deciduous teeth

20 teeth; first appear at 6 months of age

Permanent teeth

32 teeth; most erupt by the end of adolescence

Dental formula

shorthand; way to indicate number and position of teeth
2I, 1C, 2P, 3M (incisor, canine, premolar, molar

Crown

superior portion of a tooth

Clinical crown

Crown visible above gingiva

Root

portion of tooth embedded in the alveolar portion of jaw

Neck

crown and root meet at gumline

Cementum

covers the outermost surface of the root

Periodontal ligament

attaches the tooth to bone

Dentin

the bulk of the tooth is composed of this material. Produced by odontoblasts.

Pulp cavity

central portion of the tooth

Root canal

pulp cavity in the distal portions of the root.

Salivary Glands

3 small glands throughout tongue, palate, cheeks

what do salivary glands produce?

Produce saliva ( water, ions, mucus, and enzymes), to keep mouth moist.

Parotid glands

in the cheek area

Submandibular glands

as the name says in the area of the mandible

Sublingual glands

under the tongue

pharynx

contains the areas: Oropharynx and laryngopharynx
it is the passages for air and food; lined with stratified squamous epithelium

what type of tissue is the parynx lined with?

stratified squamous epithelium

GERD

weakness of the sphincter - heartburn, regurgitation

esophagus

is stratified squamous epithelium ( adapted for constant abrasion) has mucous glands, muscularis externa (Skeletal muscle) first third of length, differ from other areas: Adventitia—most external layer

unusual layer of esophagus

Adventitia—most external layer

Greater curvature

convex left surface

Lesser curvature

concave right surface

rugae

on internal surface of the stomach, with numerous longitudinal folds, which flattens as the stomach fills

oblique layer

helps vigorous churning, third layer of the muscularis externa

gastric pits

narrow tube like structures, mucosa dotted with them; gastric juice is secreted from gastric glands, which are located in them

Gastric glands

deep to gastric pits

fundus

top region of the stomach

Peyer's patches

They are aggregations of lymphoid tissue that are usually found in the lowest portion of the small intestine ileum (they differentiate the ileum from the duodenum and jejunum)

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