Digestive Anatomy and Processes Pt 2 Flashcards
The stomach
- a j shaped sac: temporary storage tank (2-6 hours) and site of demolition
- starts chemical digestion - the breakdown of proteins
chyme
“juice”, liquified slurry of food
Stomach volumes
empty: 1/4 cup
full: 1 gallon
rugae
mucosal folds seen in an empty stomach
Muscularis
has an added internal, oblique layer to allow increased mixing and churning - more intense mechanical breakdown
Mucosa
contains simple columnar epithelium made entirely of mucous cells - produces a cloudy, protective double layer of alkaline mucous
Gastric Glands
the glands of the fundus and body are substantially larger and produce the majority of the stomach’s secretions
Mucus neck cells
produce thin, soluble mucus
parietal cells
produce HCI and secrete intrinsic factor (required to absorb B12)
chief cells
secrete pepsinogen and lipases
pepsinogen
inactive pepsin
enteroendocrine cells
secrete chemical messengers into the lamina propria as well as gastrin
Gastric juice
a corrosive acid with the ability to digest the stomach itself
Mucosal Barrier
produced to protect the stomach
- a thick coating of bicarbonate-rich mucus
- tight junction between epithelial cells
- quick replacement of damaged mucosal cells by stem cells
gastritis
inflammation of the stamach in response to breaches of the mucosal Barrier
peptic/gastric ulcers
erosions of the stomach wall, cause gnawing, epigastric pain
- pain typically appears 1-3 hours after eating and resolves with eating again
- ulcers are linked to peritonitis and H, pylori - a type of acid resistant bacteria
propulsion
peristalsis
mechanical breakdown
churning
digestion
breakdown of proteins by HCI and pepsin (rennin in infants)
absorption
only lipid-soluble substances - alcohol and aspirin
secretion of intrinsic factor
essential for B12 absorption and maturation of RBCs
Digestive process in the stomach order
- propulsion
- mechanical breakdown
- digestion
- absorption
- secretion of intrinsic factor
How much gastric juice is secreted a day
> 3L
Neural Mechanisms of Regulation
- stimulation by the vagus nerve increases secretion
- stimulating by the sympathetic Nervous System decreases secretion
Hormonal Mechanism of regulation
- gastrin stimulates secretion of HCI by the stomach
- gastrin stimulates secretion of gastrin antagonists by the SI
Regulation of gastric secretion
control of HCI - secreting parietal cells is multifaceted - secretion is simultaneously by ACh, gastrin, histamine
3 phases of gastric secretions
- Cephalic/Reflex Phase
- Gastric Phase
- Intestinal Phase
(can happen simultaneously)
Cephalic/Reflex Phase
triggered by smell, taste, and sight; act via the vagus nerve
Gastric Phase
triggered by stretch receptors and/or chemical stimuli - partially digested protein, caffeine, rising pH
- activates G cell to secrete gastrin
- gastrin initiates release of HCI
- low pH or firing of the SNS will inhibit gastrin
Intestinal Phase
partially digested food enters the SI and triggers the release of intestinal gastrin
- distentions of the SI and.or the presence of acidic, fatty, or hypertonic chyme will inhibit secretions - protects the SI from excess acidity and being overwhelmed
- enterogastric reflex
- enterogastrones
enterogastric reflex
short reflexes by the enteric nervous system and long reflexes by the sympathetic and vagus nerve inhibit acid secretion
enterogastrones
duodenal enteroendocrine cells release secretin or cholecystokinin to inhibit gastric secretions
How long does the stomach take to empty
4 hours
how much L in the stomach before pressure rises
1.5L of food
Duodenum
prevents filling by controlling how much chyme enters - stretch and chemical receptors triggers the enterogastric reflex and enterogastrones to inhibit gastric secretions and to reduce the force of pyloric contractions
how long can fatty chyme delay stomach emptying
6 hours
causes of vomiting
- extreme stretching
- Intestinal irritants such as bacterial toxins, excessive alcohol, spicy foods, and certain drugs
vomiting… slide 11
liver
many functions, but its digestive function is the production of bile
- produces about 900mL of bile.day
- processes Bloodborne nutrients, stores fat-soluble vitamins, and performs detoxification
bile
fat emulsifier
gallbladder
chief function is the storage bile
pancreas
supplies most of the enzymes needed to digest chyme as well as bicarbonate needed to neutralize stomach acid
the liver is the body’s largest gland and weighs
3lbs
lobes (liver)
right, left caudate, quadrate
falciform ligament (liver)
separates the larger right lobe from the smaller left lobe and suspends the liver from the diaphragm and anterior abdominal wall
round ligament/ligamentum teres (liver)
remnant of fetal umbilical vein; runs along the free edge of the falciform ligament
biles pathway…(slide 14)
liver lobules
- hexagonal structural and functional units
- composed of plates of hepatocytes that filter and process nutrient-rich blood
- central vein
central vein
located in the longitudinal axis
portal triad
located in each corner of the lobule
- hepatic artery
- hepatic portal vein
- bile duct
hepatic artery
supplies oxygen to the liver
hepatic portal vein
brings nutrient-rich blood from the intestines
bile duct
receives bile from canalculi
liver sinusoids
leaky capillaries located between hepatic plates
how does blood move in the liver
hepatic portal vein and hepatic artery through the sinusoids to the central vein –> IVC
stellate/hepatic macrophages
exist in liver sinusoids to remove debris and old RBCs
bile
yellow-green, alkaline solution
what does bile contain
- cholesterol, triglycerides, phopholipids, electrolytes, bile salts, billirubin
bile salts
cholesterol derivative that function emulsification/absorptionb
billirubin
yellow pigment formed from Herne during the breakdown of RBCs
- metabolized by bacteria in the SI to sterocobillin which gives feces a brown color
enterohepatic circulation
recycling mechanism that conserves bills salts - salts are reabsorbed in the ileum and returned to the liver via hepatic portal blood
- 95% of secreted bile is recycled, 5% newly synthesized
hepatitis
inflammation of the liver
- viral infection, but can be caused by alcohol, drug toxicity or wild mushrooms
- six viruses: A-F; 2 transmitted through food, remainder via blood
cirrhosis
progressive, chronic inflammation from hepatitis or alcoholism
- liver activity is depressed
- liver becomes fatty and fibrous
- portal hypertension
portal hypertension
flow of blood through the liver is obstructed
