the digestive system

parietal peritoneum

lines the wall of the abdominal cavity

hepatocytes

liver cells that secrete bile, which is transported to gall bladder for concentration and temporary storage

papillae

small bumps found on the upper surface of the tongue

muscularis mucosae

thin layer of smooth muscle making folds to increase surface area; smooth muscle that produces local movements of mucosa

chief cells

A cell of the gastric glands that secretes pepsinogen (breaks down protein) and gastric lipase

saliva

99.5% water and 0.5% solutes, among the solutes are ions, including sodium, potassium, chloride, bicarbonate and phosphate. Also present are some dissolved gases and various orgnaic substances, including urea and uric acid, mucus immonoglobulin A

composition of saliva

99.5% water, 0.5% solutes including salts, lysosomes, salivary amylase, and mucins

visceral peritoneum

"serosa," covers some organs in the cavity and is their serosa

exocrine cells present in gastric glands

- surface mucous cells - mucous neck cells - parietal secreting HCl -intrinsic, absorption of vit B - chief or zymogenic secreting pepsinogen and gastric lipase

acini

99% the pancreas made up of small clusters of glandular epithelial cells, it makes up the exocrine portion of the pancreas, the cells within the acini secrete a mixture of fluid and digestive enzymes called pancreatic juice

anatomy of pancreas

-divided 3 parts, head, body and tail, connected to the duodenum via pancreatic duct (duct of Wirsung and duct of Santorini)

3 layers lying deep to the mucosa

-submucosa is formed of areolar CT -muscularis has 3 layers of smooth muscle, inner oblique, middle circular and outer longitudinal - serosa is part of the visceral peritoneum, the lesser curvature "lesser omentum, greater curvature "greater omentum"

the digestive system performs six basic processes

1. ingestion- eating 2. secretion- release of water, acid, enzymes into lumen 3.propulsion- churning and movement of food 4. digestion- mechanical and chemical breakdwon 5. absorption- passage of product from GI into blood , lymph 6. defication

secretion of HCl by parietal cells

1.secrete H+ and chloride ions Cl- separately= HCl 2. H+/K+ ATPases pumps transport H+ into lumen, while bringing in K+ into the cell 3. Cl- and K+ diffuse out 4. (CA)caronic anyhdarase catalyzes formation H2CO3, from water and CO2 5. H2CO3 dissociates, into H+ for proton pumps, HCO3- builds up in cytosol, it exits the parietal cell in exchange for Cl- 6. HCO3- diffuse into blood capillaries

most food leaves the stomach

2-6 hours after ingestion, carbo earliest followed by proteins and fat

gastric glands consist of

4 types of exocrine cells and one type of enteroendocrine cells.

peritoneal cavity

A space between visceral and parietal peritoneum within the abdomen that holds abdominal organs and has some fluid to reduce friction.

bolus

A term used to describe food after it has been chewed and mixed with saliva

parietal cells

Cells found in gastric glands that secrete hydrochloric acid (for hydrolysis of ingested food) and gastric intrinsic factor (for absorption of vitamin B-12).

adventitia

Esophagus

salivary gland

Glands of the mouth that produce saliva, a digestive secretion

dentiton

Humans have two dentitions, or sets of teeth: deciduous and permanent. The first of these—the deciduous teeth (baby teeth)—begin to erupt at about 6 months of age, and approximately two teeth appear each month thereafter, until all 20 are present

stomach

J shaped enlargement of the GI tract, serves as a mixing holding area, begins the digestion of protein and continues the digestion of triglycerides, convert bolus to liquid chime.

mucous neck cells

Located near the gastric pit and secret mucus

extrinsic muscle of the tongue

Originates from bone and extend to the tongue; Functions: altering the tongue's position, allowing for protrusion, retraction, and side-to-side movement.

histology of the stomach

Same layers of the GI tract mucosa, submucosa, muscularis and serosa. surface of the mucosa is a layer of simple columnar epithelial cells called surface mucous cells, lamina propria and muscularis mucosae

chemical digestion

Series of hydrolysis reactions that break dietary macromolecules into monomer carried by digestive enzymes secreted by the salivary glands, stomach, pancreas, and small intestine. A few substances can be absorbed without chemical digestion, vitamins, ions, cholesterol and water.

gastric intrinsic

Substance that is necessary for the uptake of vitamin B12?

greater omentum

The double-layered, apron-like structure that hangs from the lower border of the stomach, the largestest peritoneal fold

epithelim

The epithelium in the mouth, pharynx, esophagus, and anal canal is mainly nonkeratinized stratified squamous epithelium that serves a protective function. Simple columnar epithelium, which functions in secretion and absorption, lines the stomach and intestines. The tight junctions that firmly seal neighboring simple columnar epithelial cells to one another restrict leakage between the cells. The rate of renewal of GI tract epithelial cells is rapid: Every 5 to 7 days they slough off and are replaced by new cells. Located among the epithelial cells are exocrine cells that secrete mucus and fluid into the lumen of the tract, and several types of endocrine cells, collectively called enteroendocrine cells

mucosa

The innermost layer of the human digestive tract; contains layer of epithelium in direct contact with the content of the GI tract, a layer of CT called the lamina propria and a thin layer of smooth muscle (muscularis mocosae)

digestive system

The system of organs and structures responsible for the digestion of food. The digestive system includes two groups of organs the GI tract and accessory digestive organs.

surface mucous cells

This type of secretory cell lines stomach lumen and extends into the gastric pits

mesentery

a fan shaped fold of the peritonuem, a fold of the peritoneum that attaches the stomach, small intestine, pancreas, spleen, and other organs to the posterior wall of the abdomen

submandibular glands

a salivary gland inside the lower jaw on either side that produces most of the nocturnal saliva

intrinsic muscle of the tongue

alter shape of tongue, swallowing and speech

tongue

an accessory digestive organ made of skeletal muscle covered with mucoous membrane. Each half of the tongue consists of extrinsic and intrinsic muscles

lesser omentum

anterior fold in the serosa of the stomachand duodenum, it connects the stomach and duodneum to the liver. It is the pathway for blood vessels entering the liver and contains the hepatic portal vein, common hepatic artery and common bile duct along with lymph nodes

lamina propria

areolar CT,contain blood and lymphatic vessels, which are the routes by which nutrients absorbed into the GI tract and reach the tissues of the body. contain the cells of the mucosa associated lymphatic tissue (MALT)

gastric phase

begins when food enters the stomach, increase in PH and distension of the stomach, stimulates the chemoreceptors and mechanoreceptors (stretch), result is the secretion of gastrin (Gcell) and peristalsis by the muscularis

sodium bicarbonate

bicarbonate ions neutralize acid chyme and raise pH to slightly alkaline (pH 7.1-8) stop stomach pepsin activity and promote activity of pancreatic enzymes.

submucosa

binds the mucosa to the muscularis, contain blood and lymphatic vessels that receive absorbed food molecules, contains a network of neurons known as the submucosal plexus.

esophageal stage

bolus enters the esophagus, peristalsis, contraction and relaxation of the layers of muscularis pushes the bolus onward

voluntary stage of swallowing

bolus is forced back into the oral cavity and into the oropharynx by the movement of the tongue upward and backward against the palate.

4 anatomical subdivisions of the stomach

cardia, fundus, body and pylorus

pharynx

composed of skeletal muscle and lined by mucous membrane, divided into 3 parts nasopharynx, oropharynx and laryngopharynx. The nasopharynx function in respiration, oropharynx and laryngopharynx have digestive and respiratory functions.

walls of the esophagus

contain mucosa, submucosa, muscularis and adventita

gastrointestinal (GI Tract)

continuous tube that extends from the mouth to the anus, include mouth, pharynx, esophagus, stomach, small and large intestine

liver

divided into two lobes a large right lobe and a smaller left lobe by the falciform ligament, a fold of the mesentery

gastric emptying is inhibited by

enterogastric reflex and hormones secretin and CCK

trypsin, chymotrypsin, carboxypeptidase and elastase

enzymes in the pancreatic juice that digest protein into peptides

gastric glands

epithelial cells extend down into the lamina propria, where they form columns of secretory cells, the glands open into the bottom of a narrow channel called gastric pits

mesentery, mesocolon, falciform ligament, greater omentum and lesser omentum

extensions of peritoneum, contains large folds that weave between the viscera, the folds bind the organs to one another and to the walls of the abdominal cavity.

achalasia

failure of the lower esophagus sphincter muscle to relax, impeding entrance of food into the stomach

panreatic lipase

fat splitting enzyme

pancreatic islets (islets of Langerhans)

form the endocrine portion of the pancreas. these cells secrete hormones glucagon, insulin, somatostatin and pancreatic polypeptide.

enteroedocrine cells

hormones (secretes gastrin)

ankyloglossia

if a person lingual frenulum is abnorally short, the is said to be "tongue tied"

lingual gland

in the lamina propira of the tongue secrete both mucus and a watery serous fluid that contains the enzyme lingual lipase

accessory digestive organs

include the teeth, tongue, salivary glands, liver, gallbladder and pancreas. The teeth aid in breakdown food and the tongue assist in chewing and swallowing, the other organs produce or store secretions that flow inot the gi tract through ducts, the secretion aids in the breakdown of food.

the muscularis of the stomach has 3 layers of smooth muscle

inner oblique, middle circular and outer longitudinal layers.

mechanical digestion

involves physically breaking the food into smaller pieces

lobules

irregular hexagonal units into which liver are organized. each lobule consists of hepatocytes, sinusoid, stellate reticuloendothelial cells called kupffer cells (phagocytes) and a central vein

esophagus

is a collapsible, muscular tube lying behind the trachea connecting the pharynx to the stomach.

enteroendocrine cells

known as G cells secrete hormone gastrin into the bloodstream

digestion in the mouth

mechanical digestion or mastication, food is manipulated by the tongue, ground by teeth. Salivary amylase and lingual lipase, contribute to chemical digestion in the mouth.

what are the 4 layers of the GI tract

mucosa, submucosa, muscularis and serosa/adventitia

peritoneum

multilayered membrane that protects and holds the organs in place within the abdominal cavity

ribonuclease and deoxyribonuclease

nucleic acid splitting enzymes

muscularis

of the mouth, pharynx and superior contain skeletal muscle that produces voluntary swallowing

HCl is produced by parietal cells, this acid activates

pepsinogen to pepsin

stellate reticuloendoithelial "Kupffer's cells"

phagocytic cells of the liver; destroy worn-out white blood cells and red blood cells, bacteria, and other foreign matter in the blood draining the GI tract

deglutition

receptors in the oropharynx simulate the deglution center in the medulla and the lower pons of the brain sten

enterogastric reflex

reflex stimulated by low pH, high fat, high carb, hypertonicity, or distention in the duodenum, resulting in decreased gastric emptying

Neural negative feedback

regulates the pH of gastric juice and gastric motility during the gastric phase

Gerd

relaxation of lower esophageal sphincter (LES) with acid reflux

parotid gland

salivary gland within the cheek, just anterior to the ear

the secretion of saliva is called

salivation , is controlled by the autonomic nervous system.

G cells

secrete gastrin, stimulates parietal cells to secrete HCl and chief cells to secrete pepsinogen, lower esophageal sphincter, increase motility of stomach and relax pyloric sphincter

lingual glands

secrete lingual lipase, triglycerides broken down into fatty acids and diriglycerides

salivary glands

secrete saliva, lining of mouth and pharynx, saliva softens and dissolves food and cleanses mouth and teeth. Salivary amylase splits starch into smaller fragments (maltose)

As chyme enters the duodenum, the duodenum releases the two hormones:

secretin and cholecystokinin

cephalic phase

smell, sight, thought activates neural centers in the cerebral cortex, hypthalamus and brain stem. stimulates the gastric secretion and motility by way of vagus nerves (parasympahetic)

buccal cavity

space between teeth and cheeks

pancreatic amylase-

starch digesting enzyme in pancreatic juice

serosa

superficial layer of the GI tract, compose of areolar CT and simple squamous, also called visceral peritoneum because it forms portion of the peritoneum. The esophagus lacks a serous instead has a single layer of areolar CT called adventitia

falciform ligament

suspends the liver from the diaphragm

myenteric plexus

the ___ ___ is found between the inner circular and outer longitudinal layer and helps in mechanical processing and in the propulsion of materials along the digestive tract

deglutition

the act of swallowing, secretion of saliva and mucos and involves the mouth, pharynx and esophagus. 3 stages vouluntary, pharyngeal (involuntary) esophageal stage (involuntary)

(involuntary) pharyngeal stage

the bulos stimulates receptors in the oropharynx, impulses are sent to the deglutition center in the medulla oblongata and lower pons of the brain stem, which causes the soft palate and uvula to move upward to close off the nasopharynx, which prevents food from entering the nasal cavity, epiglottis closes off the opening to the larynx, prevents food from entering the respiratory system.

digestive activities occur in three phases

the cephalic phase, the gastric phase and the intestinal phase

mesocolon

the fold of the visceral peritoneum that surround the large intestine and attaches it to the posterior wall of the the abdominal cavity

rugae

the folds in the mucosa lining the stomach

three pairs of major salivary glands:

the parotid, submandibular, and sublingual glands

gastric emptying

the release of chyme form the stomach into the duodenum, stimulated by nerve impulses in response to the distension of stomach and stomach gastric in response to the presence of food.

pylorospasm and pyloric stenois

two adnormalities of the pyloric sphincter in newborns, block the exit f food from the stomach into the duodenum (relax the muscle sphincter for treatment of pylorospasm or surgery for pyloric stenosis)

absorption in the stomach

walls are mostly impermeable to most substance, but some water, electrolyes, certain drugs (aspirin) and alcohol can be absorbed through the lining

sublingual glands

what are the smallest of the salivary glands - these are almond shaped and buried in the anterior region of the floor of the oral cavity

gastric secretion is stimulated

when pH rises and inhibited when the PH of gastric juices goes below 2.0 (neg feedback) provides an optimal low pH (acidic) for pepsin and killing of microbes.

intestinal phase

when partially digested food enters duodenum, it triggers enterogastric reflx and secretion of secretin and cholecystokinin (CCK) by the enteroendocrine cells of the intestinal mucosa, stops the secretion of gastrin by G cells