- Mucosa: stratified squamous non-keratinizing epithelium; changes to simple columnar at the stomach
- Lamina propia: dense elastic connective tissue with a few defensive cells and maybe some mucous glands
- Muscularis mucosa: a thick band of longitudinally arranged smooth muscle
- Submucosa: contains mucous glands
- Muscularis Externa: inner is circular layer, and outer is a longitudinal layer; in the upper 1/3 it is striated for voluntary motion; the middle 1/3 is smooth mixed with striated for peristalsis; and the lowest 1/3 is purely smooth muscle
- NOTE: the mucosa technically includes the epithelium, the lamina propia, and the muscularis mucosa
What is the myenteric/Auerbach's plexus?
a nerve that lies between and innervates the two layers of the muscularis externa
What major changes occur at the esophpgeal-stomach junction?
- stratified squamous changes to simple columnar
- change from serous glands to simple tubular glands
Gross anatomy of the stomach (from top to bottom)
- Caridac region: entrance ot the stomach, nearest the heart
- Body or corpus: large central portion; cheif region of muscular grinding and production of chemicals necessary for digestion
- Anteroom: from the antrum to the pyloris; important regulatory region bc it produces hormones such as gastrin
- Pyloris: portion nearest the duodenum; has many layers of thick smooth muscle
Layers of the stomach (inside out)
- Mucosa: simple columnar epithelium; short pits with tubular glands; surface cells are mucous cells
- Muscularis Mucosa
- Muscularis Externa: three layers (outer longitudinal, middle circular, and inner oblique)
- Serosa: outermost layer with a simple squamous mesothelium
The cells of the stomach
- surface mucosal cells: covers the surface and pits; basal nucleus
- parietal cells: large with central nucleus; transport H and Cl and make instrinsic factor; present in the tubular fundic glands
- mucous neck cells: associated with parietal cells at the neck of the glands; not seen in H&E
- chief cells: at the bas eof hte gastric glands; cuboidal or low columnar; basophili; secrete pepsinogen and other zymogens
- enteroendocrine cells: scattered throughout the glands; flask-shaped with a narrow neck; dense membrane-bound granules that secrete different hormones such as gastrin, glucagon, seratonin
What are the changes that occur at the small intestine?
- mucosa changes from gastric pits to villi; made of columnar cells for absorption and goblet cells that secrete mucous
- Brunner's glands: in the submucosa of the duodenum; produce secretions that neutralize the acid and a mucous that protects the small intestine
- organization into shrot tubular glands called crypts
- paneth cells are at the base of the crypts; they have secretory granules that stain bright red; secrete lysozyme and other antibacterial substances
- enteroendocrine cells
What is the defining factor of the ileum?
Peyer's patches and Plicae circularis
What are the significant features of the Large Intestine?
- no more villie, but still has columnar epithelium with microvilli
- deep crypts and glands
- lots of lymphatic tissue
- three thick bands of muscle in the muscularis externa, called the taenia coli
Function of the pancreas
- Exocrine: acini of serous-type cells are filled with granules of mixed enzymes for secretion; makes tryosinogen, chymotrypsinogen, carboxypeptidases, elastase, amylase, lipase, lecithinase, ribonuclease, and deoxyribonuclease
- Endocrine: islets of Langerhans; alpha cells make glucagon; beta cells make insulin; delta cells make somatostatin
What is the function of the liver?
- exocrine secretion via bile ducts
- maintenance of optimal concentrations of various components of blood and filtering of the blood
What is a Kupffer cell?
phagocytic cell in the liver
What are the functions of the kidney?
- maintain water and electrolyte homeostasis
- regulate blood pressure
- endocrine function: production of erythropoetin for RBC formation, renin for BP control, and modification of Vit D to its active form
The functional units of the kidney
- Renal corpuscle: glomeruli + Bowman's capsule
- Nephron: renal corpuscle + tubule
- Uriniferous tubule: nephron + collecting duct
Proximal convoluted tubule
- receives the gomerular filtrate
- primary site for resorption of useful sugars, small proteins and salts
- cuboidal cells with brush border and mitochondira rich infoldings
- active movement into the cells but passive movement from cells to nearby peritubular capillaries
Distal Convoluted Tubule
- cuboidal cells with diminished brush border
- clear cytoplasm
- sodium and water resorption
- sensitive to ADH
Loop of Henle
- between the PCT and DCT
- responsible for osmotic gradient in the interstitium of the medulla necessary for the resorption of water
- surrounded by interstitial tissue and collecting ducts
- receive the urine from the DCT
- clumped to form medullary rays
- impermeable to water in the absense of ADH
The cells of the pars distalis and intermedia and thier products
- Somatotrophs: Growth Hormone
- Thyrotrophs: thyroid stimulating hormone
- Gonadotrophs: FSH and LH
- Lactotrophs: prolactin
- Corticotrophs: adrenocorticotropic hormone and melanocyte stimulating hormone
- Folliculostellate cells: may be stem cells
What does the par nervosa release?
- Antidiuretic hormone (ADH) and oxytocin
- both are made by the hypothalamus and transported down into the posterior pituitary and stored there until they are released into the blood stream
What are the two cell types in the thyroid?
- 1. follicular: single layer of cuboidla cells forma bag full of colloid; make inactive thyroglobulin and recruit iodine
- 2. parafollicular: aka clear/c cells; make calcinonin to lower blood calcium
What are the two cell types found int he parathyroid?
- 1. Chief/principal cells: majority of cells; synthesize and secrete parathyroid hormone; their cytoplasm stains
- 2. Oxyphil cells: function unclear; smaler dark nucleus and clear cytoplasm
Structure of the Adrenal glands (from outward in)
- 1. zona glomerulosa: clumps or bakks of cells right underneath the capsule; secrete the mineralocorticoids, mostly aldosterone
- 2. zona fasiculata: bubbly appearance because of lipids; secretes the glucocorticoids, like cortisol
- 3. zona reticularis: dense layer of cells; secretes the andrgens
Medulla: chromaffin cells; store the catecholamines such as epinephrine and norepinephrine; controlled by neurons and secrete their contents when sense acetylcholine
What does the pineal gland do?
- Pinealocytes: synthesize and release melatonin which regulaes circadian rhythms and scavenges hydroxyl radicals
- NOTE: Brain sand is dark and function unknown; can't see brain dust