MA Flashcards
formation of exocrine glands and their components
formation: form as invaginations of epithelium but still have a connection to the surface known as a duct
components: secretory portion (acinus of cells) and conducting portion (duct)
classification of glands
- single-cell
- simple (single unbranched duct and branched or unbranched secretory portion that’s tubular or acinar)
- compound (multiple branched ducts and acinar, tubular or tubuloacinar secretory portion)
types of secretion
- holocrine: lysis (ex: sebaceous glands on skin)
- apocrine: shedding of apical cell segment (ex: mammary glands)
- merocrine/eccrine: exocytosis of proteins or glycoproteins (ex: sweat glands, salivary glands, exocrine pancreas)
serous cells of salivary glands
secrete proteins, stain with H&E and has secretory granules in the apical cytoplasm
mucous cells of salivary glands
secrete mucins, made of glycoproteins and complex carbs, satins with PAS and has mucin-filled secretory granules in the apical cytoplasm
myoepithelial cells of salivary glands
located in the basal lamina along with secretory or duct cells with long actomyosin-rich processes which contract to help expel secretory product
*in sweat, salivary and mammary glands (merocrine cells)
what type of gland is a goblet cell?
mucin-secreting unicellular gland
3 types of multicellular simple glands
- sebaceous glands
- eccrine sweat glands
- apocrine sweat glands
sebaceous gland
- spherical or pear-shaped
- simple branched acinar differentiated from sebocytes
- holocrine secretion
- associated with hair follicles
- origin of acne
apocrine sweat glands
- simple coiled glands
- lined by simple cuboidal to columnar epithelium
- axillary, areolar, perineal regions
- MEROCRINE and phermone secretion
- associated with hair shafts
- stimulated by adrenergic fibers of the SNS
eccrine sweat glands
- simple coiled/tubular
- stratified cuboidal epithelium
- stimulated by cholinergic fibers of SNS
- 3 cell types: pale cells (secrete fluid), dark cells (secrete proteins), myoepithelial cells (triangular nucleus and contracts to expel products)
salivary glands
- a-amylase for carb digestion
- lysozyme, lactoferrin and sIgA for immune defense
- Ca2+ and P to protect teeth through pellicle formation
- PNS stimulates, SNS inhibits
- septa divides parenchyma into lobules which contain salivons (acini, intercalated ducts and interlobular ducts)
draining of acini
acini–> intercalated ducts (no secretory vesicles, cuboidal)–> intralobular ducts (inside lobules, columnar, active transport of ions and sIgA)–> interlobular ducts (in septa, stratified cuboidal to columnar epithelium)
sIgA secretion
dimeric IgA is secreted by plasma cells while serous cells and intralobular ducts have IgA receptors which mediate transcytosis of IgA into gland lumen and then sIgA is formed when the IgA and receptor complex is acted on by proteolysis
3 multicellular compound glands: salivary gland types
- submandibular
- parotid
- sublingual
submandibular gland
- compound tubuloacinar
- serous (secretes proteins), mixed and mucous acini
- *-striated intralobular ducts
parotid gland
- compound acinar
- serous acini (secretes a-amylase)
- *-intercalated ducts are long and abundant
- abundant adipose tissue
- striated intralobular ducts
sublingual gland
- compound tubuloacinar
- *-primarily mucous acini
- intralobular ducts are not striated
exocrine pancreas vs. endocrine pancreas
exocrine:
- compound acinar gland
- secretory products: digestive proenzymes activated by enterokinase and bicarbonate which neutralizes stomach acid for an optimum pH for pancreatic enzymes
- creates protease inhibitors
endocrine:
-islets of Langerhans
what does septa contain?
blood vessels, lymphatics, nerves and ducts
adenocarcinomas
malignant tumors of glandular epithelia
what is the stroma made up of?
septum (separates lobules) and capsule (surrounds gland)
sebum composition
triglycerides, cholesterol, squalene and wax esters
serious demilune
in mixed acini of sublingual and submandibular glands and secretes lysozymes
basal striations
found in intralobular ducts and are basal membrane infoldings the house the mitochondria
4 principal layers
mucosa, submucosa, muscularis externa and serosa/adventitia
3 subdivisions of the mucosa and its primary functions
subdivisions: lining epithelium, lamina propria (loose CT, blood and lymphatic vessels, lymphatic tissue, plasma cells, eosiniphils) and muscularis mucosae (creates ridges for absorption)
functions: protection, absorption, secretion
submucosa and what is unique about it in the duodenum
- dense irregular CT
- submucosal or Meissener’s plexus
- in the duodenum, it has glands
muscularis externa
- inner circular layer and outer longitudinal layer
- myenteric or Auerbach’s plexus is located between the two layers
- contraction to mix and propel contents
serosa or adventitia
serosa: simple squamous epithelium
adventitia: part of the digestive tract si fixed directly to the abdominal wall or pelvic wall
tongue
- elevations: lingual papillae
- 3 bundles of skeletal muscle
- mucosal glands, serous glands and adipose tissue between bundles
papillae (4 types)
stratified squamous keratinized without taste buds:
-filiform
stratified squamous with taste buds (sensory):
- fungiform
- foliate
- circumvallate
esophagus
- stratified squamous epithelium
- esophageal cardiac glands
- submucosa: CT and esophageal glands proper
- upper 1/3= skeletal muscle, middle 1/3= skeletal and smooth muscle, lower 1/3= smooth muscle
- adventitia above diaphragm and serosa below
esophageal cardiac glands vs. esophageal glands proper
esophageal cardiac glands: in mucosa and secrete neutral mucus (more prominent near stomach)
esophageal glands proper: in submucosa and secrete acidic mucus, facilitates food transport and protects epithelium
muscles of the UES vs. LES
UES: circular skeletal muscle, voluntary
LES: thickened circular smooth muscle, involuntary
function of the stomach
- mixed exocrine and endocrine organ
- digestion of : carbohydrates (amylase), proteins (pepsin) and triglycerides (gastric lipase)
- adds and acidic liquid
- forms chyme with enzyme and muscular activity
4 regions of the stomach
cardia, fundus, body, pylorus
*body and pylorus are very similar to each other and can’t be distinguished
rugae
temporary longitudinal folds of the mucosa and submucosa that disappears when the stomach is full
components of the stomach mucosa and their functions/characteristics
- lining epithelium: simple columnar
- gastric pits: permanent invaginations in lamina propria that serve as ducts for the mucosal glands
- mucosal glands: branches tubular glands
- lamina propria: vascularized and cellular
- muscularis mucosae: two layers
- submucosa: no permanent folds
- muscularis externa: extra layer–> inner oblique
- serosa
***mucosal glands (what they each have and their types)
each have: isthmus, neck and base
types:
1. cardiac (short pits, short coiled glands, produce mucus, some lysozyme and some HCl)
- gastric/fundic (medium pits, long straight glands, four major cell types: mucous neck cells, parietal (oxyntic) cells, chief cells, enteroendocrine cells)
- pyloric (long pits, short slightly coiled glands, mucous cells, few parietal cells, few enteroendocrine cells)
*surface mucous cells
-secretes bicarbonate (insoluble, cloudy mucus)
*mucous neck cells
-secretes soluble mucus between parietal cells in the neck of gastric glands
*parietal (oxyntic) cells
- secretes HCl and intrinsic factor (a glycoprotein required for vitamin B12 absorption in the ileum)
- large eosinophilic cells in the middle and upper part of the gastric gland
- binucleate
- intracellular canaliculus for HCl secretion
*chief cells
- synthesize pepsinogens and gastric lipases
- columnar
- found in basal half of gastric glands
*enteroendocrine cells
- produce gastrin, somatostatin and ghrelin as a single cell or in groups
- base of gastric glands
- products are both in paracrine and endocrine signaling
*stem cells
- found in isthmus and neck of mucosal glands
- replace surface mucous cells by moving upward (1x week)
- replace glandular cells by moving downward (1-2 months)
what is responsible for cilia movement?
muscularis mucosae
what helps with the ability to talk?
crisscrossing of skeletal muscles
advantage of omeprazole
you don’t get intrinsic factor secretion inhibition (advantage for long-term use)
different cilia lengths
stereocilia- longest (in sperm)
brush border- medium length
striated border- shortest (microvilus)
what 3 structures increase the luminal surface area?
- plicae circularis: permanent transverse folds of mucosa and submucosa (2-3x increase)
- villi: finger-like projections of surface epithelium and lamina propria (10x increase)
- microvilli: projections of the apical plasma membrane (20x increase)
crypts of Lieberkuhn
intestinal simple tubular glands that extend from the surface epithelium down to muscularis mucosae
6 major cell types of the epithelium
- absorptive cell
- goblet cell
- enteroendocrine cell
- paneth cell
- stem cell
- M (microfold) cell
absorptive cell
- columnar
- secretes disaccharides and peptidases which bind to microvilli and produce monosaccharides and AA for absorption
- absorb lipids which are reesterified to triglycerides and converted to chylomicrons and released from lateral surfaces to the lamina propria where they are absorbed by the central lacteals
goblet cell
- unicellular
- produce acid glycoproteins of the mucin type the protect and lubricate
- less abundant in duodenum
- increased as you approach ileum
enteroendocrine cell
- 2 types: closed (no portion exposed to lumen) and opened (has area exposed to lumen which decides if contents should be released to vessels)
- synthesize hormones and vasoactive peptides
- clear cells near base of gland (basal portion of the crypts of Lieberkuhn)
paneth cell
- immune defense
- exocrine cells found in small groups at the base of crypts
- apical cytoplasm has granules with lysozyme, phospholipase A2, hydrophobic peptides (defensis) for antimicrobial activity
- disorder= Crohn’s disease
stem cell
- differentiation as moves up to repopulate crypts
- located at base of crypts
- prevents bleeding from vessels of lamina propria into SI during radiation
M (microfold) cell
- only found in ileum
- covers Peyer’s patches
- discontinuous basement membrane (easier for lymphocytes to pass through and receive antigen from M cells)
GALT
- prominent in lamina propria
- makes up 25% of mucosa
- Peyer’s patches
- plasma cells synthesize IgA which binds to SC (secretory component) to create sIgA
regional differences in small intestine
duodenum: Brunner’s glands in submucosa and folds which secrete alkaline mucous protecting the stomach and providing an optimum pH for pancreatic enzymatic action; adventitia since retroperitoneal; villi resemble thick cactus leaves
jejunum: plicae circularis, longer more finger-like villi, more goblet cells, serosa since intraperitoneal
ileum: Peyer’s patches, longest villi and most amount of goblet cells
5 subdivisions of the LI
- colon
- cecum
- appendix
- rectum
- anal canal
colon and cecum
- temporary folds (plicae semilunares) of mucosa and submucosa
- no villi
- crypts lined with simple columnar epithelium
- lots of goblet cells
- taenia coli with thin layer of longitudinal smooth muscle in between the 3 bands
vermiform appendix
- fewer shorter crypts compared to colon epithelium
- lamina propria has lymphoid cells and lymph nodules
- submucosa= frequently edematous
- serosa
- muscularis externa has 2 complete thin layers with no taenia
rectum
-2 parts: upper rectum and anal canal
- upper rectum: like colon but less lymphoid tissue and no taenia coli; simple columnar
- anal canal: changes to stratified squamous without crypts or muscularis mucosae and then changes to stratified squamous keratinized with apocrine sweat glands (circumanal glands)
which parts of the colon have adventitia and which parts have serosa?
adventitia: ascending colon, descending colon, cecum
serosa: transverse colon and sigmoid colon
what muscles make up the internal anal sphincter and the external anal sphincter?
internal: circular smooth muscle
external: skeletal muscle
why do villi become chubby?
they have absorbed lipids
what do the stem cells replace in the stomach and in the small intestine (and how long does each replacement take)?
stomach: (located in isthmus and neck of mucosal glands)
1. replaces surface mucous cells (1 week)
2. replaces glandular cells (1-2 months)
small intestine: (located at base of crypts)
- replaces crypts and villi (3-6 days)
- replaces paneth cells (30 days)
what is the liver enclosed in and what are the 4 parts of the liver?
enclosed in: fibrous CT- Glisson’s capsule
4 lobes: right, left, quadrate, caudate
6 functions of the liver
- synthesis of circulating plasma proteins
- storage and conversion of vitamins A, D, K and iron
- degradation of drugs and toxins
- involvement in metabolic pathways
- bile production (exocrine)
- endocrine functions
how does the liver detoxify?
hepatocytes oxidize or conjugate water insoluble drugs and toxins to make them more easily removable by the kidney
which metabolic pathways is the liver involved in?
glycogen storage, cholesterol metabolism and urea synthesis
what is bile made out of?
- wastes of erythrocyte destruction
- bile salts that act as emulsifying agents to aid gut absorption
endocrine-like functions of the liver
- modifies the action of hormones released by other organs (vit D and thyroxine conversion)
- production of GHRF (growth hormone-releasing factor)
blood supply to the liver
- dual supply: hepatic portal vein (75% of liver’s blood V and is depleted of oxygen) and hepatic artery
- portal triad
- sinusoids arranged around central vein which empties into sublobular veins that join to form hepatic veins that empty into IVC
structural organization of the liver
- parenchyma: hepatocytes separated by sinusoidal capillaries
- CT stroma: continuous with Glisson’s capsule
- sinusoidal capillaries: separates hepatocytes
- perisinusoidal spaces (spaces of Disse): between sinusoidal epithelium and hepatocytes
classic liver lobule
hexagonal cylinder connecting the portal canals with the terminal hepatic venule in the center
portal lobule
triangle formed by connecting lines between central veins with portal canal at the center with exocrine functions (bile secretion)
liver acinus
football shape with long axis drawn between 2 central veins and short axis between 2 portal canals
- 3 elliptical zones
- provides insights into blood perfusion, metabolic activity and liver pathology
hepatic sinusoids
discontinuous sinusoidal capillaries that have large fenestrae and large gaps between neighboring cells
*portion of the wall of sinusoids is filled by Kupffer cells
perisinusoidal space (space of disse)
exchange of materials between blood and liver cells since the microvilli of hepatocytes project into there
*Ito cells (store hepatic vitamin A)
3 elliptical zones (liver acini)
1= heptaocytes first to receive oxygen, first to die and first to regenerate 2= intermediate in character between 1 and 3 3= first to show ischemic necrosis and first to show fat accumulation
Kupffer cells
derived from monocytes and are members of the MPS (monoculear phagocytotic system) which destroy aged erythrocytes, digest hemoglobin and destroy bacteria (15% of the liver population)
chronic inflammation and cirrhosis and Ito cells of the perisinusoidal space
Ito cells will lose the ability to store vitamin A and transform into myofibroblasts that synthesize the collagen resulting in liver fibrosis
hepatocytes
polygonal, long 5 month lifespan, replaced by regeneration, 20-30 microns in diameter, 80% of the liver population, nuclei that are large, spherical and centrally located
how do hepatocytes change with age?
binucleate cells and polyploidy nuclei develop with age
regeneration ability decreases
cytoplasmic components of hepatocytes
numerous mitochondria, elaborate Golgi apparatus, highly developed RER and SER, numerous peroxisomes and lysosomes
bile canaliculus
small canal between surfaces of adjacent hepatocytes emptying into intrahepatic ductules (canals of Hering) within lobule close to portal canal and joins with interlobular bile ducts (part of triad)
what does bile consist of?
water, phospholipids, cholesterol, bile salts (help with lipid digestion and absorption), bile pigments, electrolytes
bilirubin glucuronide
bile pigment that comes from hemoglobin breakdown excreted with feces and provides their color
what increases bile flow?
CCK, gastrin, motilin, PNS
cystic duct
receives diluted bile from the liver and discharges concentrated bile to the duodenum via the common bile duct and sphincter of Oddi
what doesn’t the gallbladder have?
muscularis mucosae
