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The Stomach

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by

Alexis Armijo

on 13 March 2014

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Transcript of The Stomach

The Stomach
What is the Stomach?
pouch-like organ that hangs inferior to the diaphragm
has a capacity of about 1 liter
receives food from the esophagus, mixes the food with gastric juice, initiates protein digestion, and moves food into the small intestine
Parts of the Stomach
Gastric Secretions
3 types of secretory cells:
Steps to breaking down food
4 Main Parts
Cardia:
small area near esophageal opening
Fundus:
temporary storage unit; balloons superior to the cardia
Body:
main part of stomach
Pylorus:
two parts-
Pyloric Antrum:
bottom of stomach nearing pyloric canal
Pyloric Canal:
narrowing part as it approaches small intestine

2 Sphincters
Cardiac Sphincter:
smooth muscles where the esophagus joins the stomach, allowing food to pass into the stomach
Pyloric Sphincter:
where the stomach joins the small intestine, the muscles allowing food to pass into the small intestine
Regulation of Gastric Secretions
gastric juice is produced continuously but the rate varies and is controlled both
neurally
and
hormonally
when a person tastes, smells, or sees food, or when food enters the stomach, parasympathetic impulses stimulate release of
Acetylcholine (Ach)
from nerve endings
Ach stimulates gastric glands to secrete abundant gastric juice
these parasympathetic impulses also stimulate certain stomach cells to release peptide hormone
Gastrin
, which increases activity of gastric glands
as food moves into the small intestine, acid triggers sympathetic nerve impulses that inhibit gastric juice secretions
at the same time, proteins and fats in this region of the intestine cause intestinal wall to release peptide hormone
Cholecystokinin (CCK)
this hormonal action decreases gastric motility as small intestine fills with food
Gastric Absorption
gastric enzymes begin breaking down proteins but stomach wall is not well adapted to absorbing digestive products
stomach absorbs only small volumes of water and certain salts as well as certain lipid-soluble drugs
Alcohol, not a nutrient, is absorbed both in the small intestine and stomach
Mixing and Emptying Actions
following a meal, mixing movements of stomach wall aid in producing semifluid paste of food particles and gastric juice called Chyme
Peristaltic
waves push chyme toward pylorus and as chyme accumulates near pyloric sphincter, this muscle begins to relax
stomach contractions push chyme a little at a time into the small intestine
rate at which stomach empties depends on fluidity of chyme and type of food present
as chyme enters duodenum, the pancreas, liver, and gallbladder add their secretions
Vomiting
vomiting results from a complex reflex that empties stomach in reverse of normal direction
irritation or expansion in stomach or intestines can trigger vomiting
sensory impulses travel from site of stimulation to vomiting center in Medulla Oblongata, and motor responses follow
taking deep breath, raising soft palate, closing opening to trachea, relaxing muscle fibers at base of esophagus, contracting diaphragm downward, contracting abdominal wall muscles
as a result, stomach is squeezed from all sides, forcing its contents upward and out
Ulcers
area of stomach irritated from exposure to gastric juices due to lack of mucus in that area
open sore in skin or mucous membrane resulting from localized tissue breakdown
associated with stress until around 1982
treated with a short course of antibiotics, often combined with acid lowering drugs
Stomach Cancer (Gastric Cancer)
Acid Reflux
Fun Facts
Stomach lining is regenerated about every 2 weeks
when you blush, inside of stomach turns red
starfish can turn its stomach inside out
moths don't have a stomach
people can live without a stomach
Pepsi is named after pepsin, the digestive enzyme in the stomach
http://www.today.com/video/today/49238269#49238269
Mucous Cells
What do they secrete?
A viscous, alkaline secretion that coats the inside of the stomach wall; prevents the stomach from digesting itself
Where are they located?
causes about 700,000 deaths worldwide per year
can be asymptomatic or have no apparent symptoms
symptoms can be similar to those of minor illnesses
by the time symptoms occur the cancer has already progressed into later stages
in most cases is caused by helicobacter pylori
In 2013 Chinese and Israeli scientists reported a successful pilot study of a Breathalyzer-style breath test intended to diagnose stomach cancer by analyzing exhaled chemicals without the need for an intrusive endoscopy,
in necks of the glands; near openings of gastric pits
Chief Cells
What do they secrete?
secretes pepsinogen- the inactive enzyme precursor to pepsin
Where are they located?
in the deeper parts of the gastric glands
Parietal Cells
What do they secrete?
in the middle of the gastric glands
Where are they located?
Hydrochloric acid; aids in the activation of pepsinogen

Intrinsic factor; helps the small intestine absorb B12
pain is caused by holes in the mucosal lining of the esophagus due to regurgitation of stomach acid
symptoms include heartburn, pain with swallowing, increased salivation, nausea, chest pain and coughing
factors that may contribute to acid reflux include obesity, gall stones, hernias, viceroptis
products of these cells together form Gastric Juice
Gastric Glands: glands in the stomach wall that secrete gastric juice
1. Chief cells in the stomach wall secrete
pepsinogen
and parietal cells secrete
hydrochloric acid
2. when these two secretions mix, the HCl breaks down pepsinogen, forming the enzyme
pepsin
3. pepsin begins
chemical
digestion in the stomach by splitting proteins and digesting them into
polypeptides

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