GIT Flashcards
general structure of GIT
layers:
TUNICA MUCOSA: epithelium lining (st sq epi for oral cavity, pharynx, oesophagus, and anus); st columnar epi (stomach (mucus), intestine (absorptive+apical specialization)
Lamina propria mucosae: loose CT, lymphatic tissue+ lymphoctes, vessels, glands, MALT (in stomach+intestine?)
Lamina Muscularis mucosa: separate mucosa from submuscularis; smooth m cells (inner circular and outer longitudinal)
TUNICA SUBMUCOSA: loose CT (denser than previous), larger blood+lymphatic vessels, Meissner (fibre-rich, submucosal) plexus, glands (oesophagus+ duodenum)
TUNICA MUSCULARIS EXTERNA
Smooth m (inner circular+outer longitudinal): in oesophagus smooth+sk m; stomach has inner oblique middle circular and outer longitudinal; between both in CT has myenteric plexus (Auerbach’s plexus) autonomic neurons into small ganglia+interconnected by pre+postganglionic nerve fibers; blood and lymph vessels
both plexus = enteric nervous system contraction of muscularis to propel lumenal contents
TUNICA ADVENTITIA
Loose CT, connects to organ, (oesophagus+anus), blood+lymphatic vessels. Lacks mesothelium. where digestive tract not suspended in cavity
TUNICA SEROSA
loose CT covered by simple sq epi (mesothelium). rich in blood+lymphatic vessels+ adipose tissue; serosa continuous w mesentery (thin membrane covered by mesothelium on both sides) and continuous peritoneum (covers and cavity).
oral cavity
oral cavity
mastigatory mucosa: stratified sq epi keratinzed- protects oral mucosa, best developed in gingiva+ hard palate
lining mucosa: non keratinized- covers soft palate, lips, cheeks, pharynx, and floor of mouth. has minor salivary glands in submucosa
parakeratinization: retain nuclei after shedding old epi
- lip - orbicularis oris m (speech, ingestion) - external zone is thin hairy skin (epidermis+dermis)- hair follicles, sebaceous +eccrine glands, - transitional zone is vermilion zone- red colour rich vasc papillary layer of dermis (capillaries+ sensory inn) . thin, lightly keratinized epidermis. NO SALIVARY OR SWEAT GLANDS (kept moist from saliva of tongue)=open directly to mucosa not hair - inner surface is oral lining mucosa: thick str sq epi-non keratinized; LP (loose CT) - submucosa: labial glands/minor salivary glands: compound tubuloacinar seromucosa glands Tansparency of lip protein-eleidin
tongue
mass of STRIATED M (and adipose tissue) covered by mucosa, fibers oriented in all direction=high level of MOTILITY (F: manipulate ingested material by mastication and swallowing). CT between small fascicles of m penetrated by LP making mucous membrane firmly adhere to muscular core.
parts: root, body, apex, dorsal and ventral
ventral: lining mucosa,smoooth (NON KERATINIZED STRAT SQ epi) w NO SUBMUCOSA
dorsal: irreg, w hundreds of small protruding lingual papillae (extensions of
LP)+ specialised mucosa (taste buds) on anterior 2/3 and + massed lingual tonsils+ lymphoid tissue (LP) on post 1/3 or root of tongue. Both areas separated by sulcus terminalis (V shaped groove).
lingual salivary glands:
1) seromucous ant lingual gland
2) serous Ebner’s gland (duct open circumvallate)
3) mucous Weber’s gland (duct open lingual tonsil)
Lingual papillae
- Filiform: SMALLEST+ most numerous. ant doral surface. conical+ elongated. CT base + heavely keratinized (white/greyish appearance) str sq epi. NO TASTE BUDS. F: pointed so provide FRICTION for mov of food
- fungiform: less numerous+ lightly/non-keratinized. ant dorsal surface. Interspersed and projects above filiform papillae. mushroom-shaped+ vasc +innervated cores of LP. has taste buds at dorsal surface of papillae
- foliate: on posterior lat edge. best developed in younger individuals/rudimentary. *Parallel low ridges separated by deep mucosal clefts. taste buds in lateral epi
- circumvallate: LARGEST, 1 -3mm, 8-12 in front of terminal sulcus. dome-shaped, surrounded by deep groove. strat sq epi-. ducts of EBNER’S glands empty to groove. (gives continuous fluid flow over taste buds, washing away food, so taste buds receive new gustatory sensation). *secretions have LIPASE, prevents formation of HYDROPHOBIC FILM on structures that hinder gustation.
taste buds: ovoid w str sq epi; 250 on circumvallate papillae; on dorsal+lat surface and continuous flushed by minor salivary glands. 5-100 gustatory cells, 7-10 d lifespan. has supporting cells (immature),
basally: slowly dividing STEM cells (Regeneration). base of taste bud on basal lamina entered by AFFERENT sensory axon that form synapses w gustatory cells.
apically: MICROVILLI project onto 2um taste pore. tastants dissolve onto saliva and contact microvilli through pore and interact w receptors.
5 cat: salty (Na), sour (H)=ion channels, sweet (sugar), bitter (alkaloids+toxins), aa-glutamate+ aspartate (umami-savory)= G protein coupled receptors
receptor binding= depolarization stimulate sensory fibers
Oesophagus
muscular tube 25cm trasnporting food from pharynx to stomach
TUNICA MUCOSA
str sq non keratinized epi, LPM has OSESOPHAGEAL CARDIAC glands =simple branched tubular mucous glands in cardia junction between stomach and oesophagus.
TUNICA SUBMUCOSA
LONGITUDINAL FOLDS, OESOPHAGEAL glands (also simple branched tubular mucous glands?)-empty into ducts in LP
TUNICA MUSCULARIS EXTERNA
inner circular and outer longitudinal; upper third has STRIATED m (sk); middle third has both; lower third has smooth m
TUNICA ADVENTITIA
loose CT, nerve fibers
TUNICA SEROSA
smallest portion 1-2cm of oesophagus
teeth
enamel+dentin
permanent teeth 32, two bilaterally symmetric arches in maxilla and mandible.
(2 incisors, one canine, two premolars, three permanent molars). primary teeth =milk teeth (20).
Structure: crown (above gingiva covered by enamel), neck (at gingiva by cemento-enamel junction) and root (dental alveolus anchors tooth to jaw, covered by cementum). Most of roots and neck consists of dentin. Pulp cavity (Neural crest cells derived) highly vasc+ well innervated, enters tooth through apical foramen. Has loose mesenchymal CT, ground substance, thin collagen fibers, fibroblasts and mesenchymal stem cells.
supporting structures: Periodontal ligaments: holds tooth to bone of jaw. alveoli is socket for tooth in mandible and maxilla. Gingiva is oral masticatory mucosa-str sq epi keratinized? (around tooth neck)
ENAMEL
ameloblasts (tall polarized cells, secrete matrix components part of enamel organ)+ from ectodermal lining of oral cavity, ameloblast apical ends contact dentin
- enamel organ is specialised epi in tooth bud: has apical ends that face odontoblast produce PREDENTIN. ameloblast extension=Tomes process have secretory granules w proteins of enamel matrix
acellular-hardest comp of human body
enamel is part of dental crown
- matrix
mineralized: 96% inorganic salts (HA hydroxyapatite, CaF2, CaCO3, MgCO3)
fluoride by HA= resistant to acidic dissolution caused by microorganism
little organic material: non-collagenous proteins: amelogenin, ameloblastin, enamelin, tuftelins and water - enamel rods=prism equals product of one ameloblast
hexagonal/keyhole shape (2-2.5mm x 4um wide x 8um high)
each 5um=d; interlocking columns crucial for enamel hardness+resistant to P during mastication. Parallel arrangement of HA, needle/leaf shaped 40-60nm x 30nm wide and 2nm thick - interrod enamel: between rods fusing them, HA have diff arrangement
- enamel striation: rhythmic growth, cyclic secretion of ameloblast = Lines of Retzius; different orientation in corse of rods (radial, spiral, radial)=Lines of Hunter Schreger
Dentin-most abundant
70% inorganic salts HA crystals
organic matrix: similar to bone (collagen I, ground substance: chondroitin+ keratan sulphate proteoglycans, osteocalcin, dentin phosphoprotein+ sialoprotein)
- granular layer of Tomes=dental striation: below cementum; arrangement of collagen+ noncollagenous proteins, non-mineralised (hypomineralised=interglobular dentin)
- odontoblast: mesenchymal origin, lines pulp cavity, produces predentin (newly secreted non mineralised dentin: has GER, GA, mito) reduces size of pulp cavity
Tomes processes extend into (longer the thicker the dentin) in dentinal tubules (odontoblast not in dentin but process insert to dentin). = maintenance matrix+repair dentin.
Columnar, apical junctional complex.
Matrix vesicles Ca and PO4 2- ions + microtrubules - intertubular dentin (between) and peritubular dentin (around dentinal tubules+ more mineralised).
- primary dentin (before eruption) secondary dentin (after root formation) and tertiary dentin (carriers, dental procedures)
- dental pulp loose CT, highly inn (feel pain)+vasc enter tooth through apical foramen; pulp horns for teeth w more than 1 cusp. has fibroblast, fibrocytes, lymphocytes, macrophages, plasma cells. heat, cold and acidic pH perceived as pain. nerves+vessels extend from odontoblast processes into dentin tubules. stimuli affects the fluid inside affecting vessels causing tooth sensitive.
cementum
cementum: root+neck, avasc, bone like=highly resistant
- matrix: 65% mineralised HA, collagen I,III, sialoprotein, osteocalcin and osteonectin.
cementocytes: in lacuna process in canaliculi, thickest around root. F: maintain surrounding matrix and gradually remodel
lower root: cellular cementum and upper root acellular cementum
cemento-enamel junction
cementum overlaps enamel 60%
cementum and enamel touch 30%
gap 10%
peridonteum=structures responsible of maintaining teeth in alveolar bone (cementum, lig, alveolar bone and gingiva)
periodontal lig: 150-350um) joins tooth (cementum) to alveolar bone.
Dense CT (ligs)+loose CT (high in blood vessels, nerve ending)+ highly cellular/
- bundles of collagen fibers, fibroblasts and elastic fibers
- principal part: alveolar crest, horiz, oblique, apical and interradicular
- gingival part: transseptal, dentogingival, alveogingival and circular and dentoperiosteal
- decreases w aging
F: tooth attachment=fixation, support, bone remodeling and proprioception, permits limited mov of tooth + helps protect alveolus from P of mastication
alveolar bone
immediate contact to periodontal lig serving as periosteum
primary bone: collagen fibers not arranged like typical lamellar pattern (adult bone)
has osteoblast and osteocyte for continuous remodelling in matrix
collagen fibers bundles of peridontal lig penetrate bone and bind to cementum
gingiva- free or attached gingiva. F: protects periodontal lig. keratinised oral mucosa of gingiva binds to periosteum of maxilla+mandible
- gingival sulcus- where oral mucosa meets tooth (between gingiva and enamel-young and gingiva and cementum-older). 0.5-3mm deep surrounding neck. has specialised part of epi=junctional epi which binds to enamel by cuticle (thick basal lamina where epi cells attached by hemidesmosomes). non keratinized
- outer basal lamina:gingival side, LP w fibroblast, lymphocytes and plasma cells
- inner basal lamina: between enamel and epi- has hemidesmosomes
stomach
cardia (narrow transitional part,1.5-3cm, between oesophagus and stomach), pylorus (funnel-shaped opens into duodenum): both are primarily involved w mucous production + are similar. Body+ fundus (sites of gastric glands=gastric juice)+ large longitudinal folds =rugae. it flattens when stomach fills food.
tunica mucosa
- GASTRIC PITS invaginations SIMPLE COLUMNAR epi (mucous secreting w BICARBONATE =protect form gastric acid+intrlalumenal foods) into LP opening to lumen
- STEM cells (pluripotent) lines pits, ducts+ lumen found in ithmus . F: injury+ regeneration of epi 4-7 days
- SURFACE MUCOSAL cells-secrete mucous rich w bicarbonate ions to keep mucosa neutral (acid don’t affect as intralumenal foods abrasive effect).
lamina propria mucosae
- pits lead to LONG BRANCHED TUBULAR GLANDS (cardiac, gastric and pyloric). where pits empty.
- vasc+lymphoid cells, lymphatics
lamina muscularis mucosa
smooth m
tunica submucosa
RUGAE FOLDS
large blood vessels, lymph vessels, LYMPHOID cells, MACROPHAGE, MAST cells.
tunica muscularis external
INTERNAL OBLIQUE M (not in cardia), middle circular and outer longitudinal
- contractions cause mixing of food+chyme w HCL, digestive enzymes from gastric mucosa
tunica serosa
thin (bc pylorus is thick due to pyloric sphincter + cover stomach)
cardia
TRANSITIONAL: strat sq non keratinized epi (oesophagus)-> simple columnar epi (secretes mucuous)
pits are SHORT+WIDE (1/4 mucosa)
CARDIAC GLANDS (in LP) =simple/branched tubular (NO PARIETAL/ CHIEF cells)
outer longitudinal and inner circular m
fundus and body
proper GASTRIC GLANDS = branched tubular
5 cells
- CHIEF cells (zygogenic): base, BASOPHILIC (rich RER+ secreting granules), secrete gastric LIPASE+ PEPSINOGEN -> pepsin (initial protein breakdown, max activity 1.8-3.5)
- *ENTEROENDOCRINE cells: base, lightly stained, paracrine+endocrine F, secrete SEROTONIN (at basal lamina of glands)+ G cells-> gastrin
secretion fo closed endocrine cell reg by content of glands indirectly. paracrine+ neural (neural receptors signal if need more)
- PARIETAL cells: in upper, middle portion; pyramidal/spherical w round nuclei (EOSINOPHILIC, abundant MITO). carbonic anyhydrase (CO2+H2O-> HCO3+ H). HCO3 goes to basal side and H w Cl transported to lumen where join. parietal cells have intracellular canaliculi (circular invag of apical p.m have microvilli).
INTRISIC FACTOR released: glycoprotein needed for uptake B12, in small intestine)
- MUCOUS NECK cells: clusters/single, less columanr than surface cells, round nuclei w secretory granules w mucous secretion is LESS ALKALINE than surface.
- stem cells
pylorus
pits are NARROW, 2/3 mucosa)
pyloric glands are BRANCHED COILED TUBULAR (NO PARIETAL/CHIEF cells)
instead are ENTEROENDOCRINE cells-> gastrin+ seratonin (5-hydroxytryptamine)
Liver
largest internal organ, 1.5kg. right upper quadrant below diaphragm, intraperitoneum. right and left lobe (major+minor). covered by thin CT capsule+ mesothelium=serous peritoneum . thicker capsule at hilum (hepatic a+portal v+bile duct+ lymphatic). stain PAS due to glycogen stored+ ALUM HEMATOXYLIN
main F: bile (emulsify, hydrolysis and uptake of fats in duodenum)+ nutrition from small intestine, stomach+ spleen processed in liver before distribution but blood is O2 poor+ produce plasma proteins (fibrinogen+ albumin, apolipoprotein, transferrin)+ stores vit A,D, K and Fe+ degradation of drugs/toxins+ glucose reg+deamination of aa-> urea
-TRABECULAE EPI : has HEPATOCYTES (arranged as radiating cords from central v- each lobule). separated by sinusoidal cap (fenestrated has pores, w out diaphragm). RETICULAR fibers. stroma- vessels, lymphatics, nerves+ bile duct)
structure:
1) CLASSIC hepatic lobule- drain blood from portal vein into hepatic a+central a (endocrine)
2) PORTAL hepatic lobule- drains bile from hepatocytes make triangular shape-> bile duct (exocrine)
3) hepatic ACINUS- supply oxygenated blood to hepatocytes (from zone 1) make diamond or irreg oval shape extending from 2 portal triads to closest central veins. zone 1 made by hepatocytes closest to hepatic arterioles (most O2+ nutritious (F: oxidative metabolism+ protein syn). zone 3 near central v least (lipid syn+glycolysis+detox-hepatoxytes here undergo fatty accumulation/ischemic necrosis-cell death)
-sinoisodal cap: fenestrated endothelial cells +discontinous +SPARSE BASAL LAMINA +RETICULAR fibres. Comes from peripheral branches of hepatic v and a to converge in central v (blood mix from both in sinusoids). central venules converge to 2 larger v-> IVC.
has KUPFFER cells=specialised/stellate macrophages (break down aged rbc, hemoglobin & Fe reused+ antigen presenting cells to remove foreign particles)
pores allow to fill narrow PERISINUSOIDAL SPACE OF DISSE (between hepatocytes and sinusoidal cap) + microvilli projecting from hepatocytes; has ITO cells (hepatic stellate cells) have small LIPID DROPLETS to store insoluble vits. are mesenchymal cells-> MYOFIBROBLAST during injury. Secrete matrix +cytokines
- Hepatocytes: 20-30um, large polyhedral cells w 2 rounded nuclei w fine chromatin+ NUCLEOLI. abundant RER, GA (plasma proteins+ bile comp), mito (eosinophilic cyto?). excessive SER, peroxisomes (oxidise FA, breakdown H2O2, purine-> uric acid) GLYCOGEN GRANULES+ LIPID DROPLETS (contain small electron dense ferritin=hemosiderin mediate storage of glucose, triglycerides and Fe). stem cell properties (compensatory hyperplasia- toxic trigger mitosis (slow rate)). OVAL cells =stem cell in bile canals.
BILE CANALICULI: where bile secreted, smallest branches of biliary trees. Between apical surface of hepatocytes joined by DESMOSOMES+ TIGHT J. Canaliculi are elongated space w 0.5-1 um lumen w large SA due to microvilli. Canaliculi form complex network of channels that end near portal tracts. canaliculi empty to CANALS OF HERING (flow opp to blood)w CUBOIDAL epi cells =CHOLANGIOCYTES which empties to r+l bile duct (cuboidal/columnar cholangocytes w CT sheath)-> common bile duct.
bile canaliculi+ bile ductules+ bile duct= common hepatic duct
bile: exocrine F, w bile acid=cholic acid, bile salts (deprotonated acid), electrolytes, Fa, phospholipids, cholesterol and bilirubin). bilirubin: pigmented breakdown product of hemoglobulin released from kupffer cells+ splenic macrophages. Bilirubin binds to albumen-> hepatocytes-> duodenum and converted to other products which secreted as urine/feaces=give its colour or absorbed by intestine.
portal triad in peripheral CT: interlobular v+ a+ bile duct (simple cuboidal epi)
Gallbladder
release 3-50mL bile; hollow pear-shaped on stored on lower surface of liver (quadrate lobe)
tunica mucosa
folded, simple tall columnar epi (covering+secretory cells and absorptive cells-bile conc, Na+K)
Rotikasnky- Aschoff sinuses: deep invagination of mucosa-> tunica muscularis
LPM: loose CT, NO GLANDS (possible near neck).
Tunica muscularis NO SUBMUCOSA/LAMINA MUSCULARIS MUCOSA
muscle fibers =inner circular+ outer longitudinal
tunica adventitia - where liver is
tunica serosa- free surface
stain: alcian blue (mucous cells)+ nuclear red for nuclei
Salivary glands
exocrine cells that produce saliva. gland surrounded by CT capsule for which parenchyma extends to divide gland to lobule.
saliva- at 6.5-6.9, minor salivary glands (encapsulated) secrete 10% of saliva, gingival sulcus, tonsillar crypts, transudation from epi lining (from pores). usually mucous except for few serous on circumvallate papillae.
Components: water, enzymes, glycoprotein, bicarbonate, Ca, P, K, Na, and PO4.
F: moisten+ lubrification; breakdown of mol; buffering (bicarbonate); digest carbs+lipids (amylase+lipase); control of bact flora: lysosomes; tooth development + maintenance + protection (Ca,PO4); immunologic function (salivary IgA)
3 types of cells:
- serous cells: POLARIZED protein+enzyme-secreting cells. pyramidal shape +round nuclei; well stained rer, apical secretory granules; joined by TIGHT+ ADHERENT junctions. form acinus w small central lumen. euchromatic w nucleoli
- mucous cells: columnar w compressed basal nuclei; apical granules w hydrophilic mucins, poor stained, tubules org. cyto has mucinogenous granule: PAS, ALCIAN BLUE
- myoepithelium cells: inside basal lamina of acini+tubules proximal ends of duct systems. contractile processes to move mucous down
duct system: secreting cells empty-> intercalated duct merge -> striated duct join-> intralobular-> interlobular-> main duct. all ducts have nerves+vessels . parasymp: smell or taste of food. sympa: dry mouth.
- intercalated ducts: SEROUS acini, simple CUBOIDAL epi; carbonic anhydrase: secrete HCO3, absorbs Cl from primary saliva
- striated duct: simple low COLUMNAR epi
EOSINOPHILIC BASAL STRIATION: structural specialisation, infolding of basal P.M -> cyto w elongated mitochondrial. F: reabsorb Cl and Na and K and HCO3 secreted to duct lumen. Primary saliva-> secondary saliva (hypotonic). - intralobular ducts: inside lobes. CT surrounding have plasma cells-> IgA which transfer to saliva having defense against pathogens.
- interlobular ducts: between lobes, pseudo columnar epi= basal cuboidal+columnar cells = 2 layers of nuclei. as diameter becomes larger= stratified sq epi
- main duct: stratified columnar epi; at oral cavity= non keratinised strat sq epi
glands
Parotid gland: cheek, near ear. BRANCHED ACINAR glands, serous cells-> alpha-amylase (carbs+ proline-rich proteins w antimicrobial properties)
submandibular gland: BRANCHED TUBULOACINAR, primary SEROUS acini conc in demilunes bc during histo prep mucous cells fuse. produces 2/3 of all saliva. basolat mem infolding of serous cells facilitate transport of water+ electrolyte. secrete (same as parotid) also lysosome (bact wall hydrolysis, pump)
sublingual glands: smallest, BRANCHED TUBULOACINAR but tubular MUCOUS cells dominate. the few serous acini in demilunes (secrete lysosome+ alpha amylase)
Pancreas
Mixed exocrine+endocrine gland. head near duodenum, body and tail near spleen. Thin CT capsule, septa extend over larger vessels+ ducts; separates it into lobules. Secretory acini surrounded by basal lamina supported by reticular fibres+ capillaries. NO STRIATED DUCTS OR MYOEPITHELIAL CELLS
endocrine function: islets of Langerhans: check
exocrine function: COMPOUND ACINAR gland (pyramidal, basal cyto w rer+ mito; GA supranuclear position, apical cyto zymogen secretory granules.)
inactive zygogens: TRPSINOGEN (activates cascade), CHYMOTRYPSINOGEN, proelactase, kallikreinogen, and procarboxipeptidase
- trypsinogen cleaved-> trypsin and activated by enteropeptidase in duodenum.
- pancreatic tissue protected against autodigestion: restrict protease activation to duodenum; trypsin inhibitor; low pH in acini+ duct due to HCO3 secreted centroacinar+ intercalated ducts to keep all enzymes inactive
intercalated duct (simple sq epi) penetrate lumen of acinus w centroacinus cells (lightly stained) -> intralobular duct-> interlobular duct (pseudo becomes bigger= str sq epi) -> main duct (str columnar epi)
pancreatic juice
rich in BICARBONATE ions (alkalize+transports enzymes), digestive enzymes = PROTEASE (inactive zymogens activated in small intestine to prevent pancreas from digesting itself), AMYLASE, LIPASE and NUCLEASE (DNA and rnatase)
secretion: 1.5L per day. Controlled by SECRETIN (promote water and bicarbonate secretions by duct cells). CHOLECYTOKININ CCK (stimulate secretion of acinar cells+ exocytosis of zymogens and enzymes) produced by enteroendocrine cells of intestine
Small intestine
long 5cm, duodenum, jejunum and ileum. The digestive processes completed where nutrience absorbed by cells of epi. 60-70% of immune cells are.
mucuos membrane has permanent folds (PLICA CIRCULARIS) to increase SA (NOT IN BULBUS DUODENI)- permanent bc supported by mucosa and submucosa (more abundant in jejunum), independent of muscle contraction
Tunica mucosa
intestinal VILLI - CT surrounded by SIMPLE COLUMNAR epi w ENTEROCYTES (brush border), GOBLET cells; center has lymphatic capillary =LACTEAL. CORE OF LOOSE CT extends into inner LPM has FIBROBLAST, LYMPHOCYTES, MACROPHAGE, PLASMA CELLS AND EOSINOPHILS and fenestrated blood capillaries.
BRUSH BORDER and enterocytes
6 types of cells:
- ENTEROCYTE: tall columnar cells w oval NUCLEUS BASALLY; MICROVILLI (BRUSH BORDER/STRIATED) covered by *GLYCOCALYX. around 3000 microvilli in one enterocyte. high SA for nutrient.
Secrete *DISSACHARIDES+ PEPTIDASE (hydralize disac+ dipeptide-> monosacc+ aa = Active transport.
Digestion of fat by gastric + pancreatic lipase -> lipid subunits-> micelles (2nm) by bile salts=passive diffusion + membrane transporters. lipids reesterified into triglycerides (smooth ER) + apoproteins (GA)= CHYLOMICRONS. discharged by basolat surface for lacteal uptake.
- GOBLET cells: between enterocytes (glucoproteins mucins which is hydrated=mucin) - PANETH cells: *basal portion of intestinal crypts. Are exocrine cells w *EOSINOPHILIC GRANULES: LYSOSOME, PHOSPHOLIPASE A, DEFENSIN (hydrophobic peptide). F: innate immune role, bind and break of microorganism+ bacteria - ENTEROENDOCRINE cells: release secretory granules. secrete peptide hormones. open w apical chemoreceptors in lumen. paracrine+endocrine; control peristalsis and secretion - M (microfold) cells: specialised epi cells (ileum) overlying lymphoid cells of peyer patches. *Basal mem contain INTRAEPI LYMPHOCYTES + APC; transport IgA; Endocytose antigens transports to dendritic/ lymphocytes -> l.n; sampling stations- mat of gut lumen to lamina propria MALT
LPM: penetrate wall of villi (to bring in microvasc+ nerves). CRYPTS OF LIEBERKUHN (short TUBULAR glands)+ PEYERS PATCHES (in ileum, lymphatic nodules)
LMM: inner circular+ outer longitudinal. contraction produce rhythmic mov of villi increase absorption eff.
Tunica submucosa: larger blood vessels+ lymph vessels+ MEISSNER n plexus
BRUNNER gland ( proximal part of duodenum, mucous): large clusters of BRANCHED TUBULAR mucous glands with small ducts open to crypts (F: ALKALINE to neutralize chyme in duodenum from pylorus) +
ileum has well developed MALT= large aggregated lymphatic nodule= peyers patches (ileum) which underlies epithelial M cells.
Tunica Muscularis
inner and outer (between MYENTERIC plexus=peristalsis).
neurons of myenteric and meissner = large enteric nervous system.
Tunica Serosa (thin mesothelium continuous w mesentery)
Large intestine+ Anal Canal
short cecum (w ilocecal valves), appendix, asc hori desc colon, sigmoid colon and rectum. diameter 6-7cm. walls have large sacs= HAUSTRA
F: absorbs water+ electrolytes transform indigestible mat-> feaces
Tunica mucosa
NO VILLI+ NO MAJOR FOLDS (except in rectum)
simple COLUMNAR epi: COLONOCYTES irreg MICROVILLI; GOBLET cell (mucous tubular intestinal glands+ more than SI); small # ENTEROENDOCRINE cells; stem cells at bottom third of each gland
LPM: long crypts of Lieberkuhn +lymphatic nodules and cells+ GALT
LMM
Tunica submucosa: lymphatic NODULES
Tunica muscularis: inner and outer (3 bands of tenia coli)
Tunica Serosa: covers, intraperitoneal + small pendulous protuberance of adipose tissue+ mental appendages
Adventitia at rectum
Anal Canal is 3-4cm
Tunica Mucosa
COLORECTAL zone: simple columnar epi
has anal TRASNITIONAL zone: strat COLUMNAR/cuboidal epi-> STRAT SQ cells of perianal skin w strat columnar epi between them. LMM DISAPPEARS (sabecous glands?)
Tunica Submucosa w tunica mucosa has SINUS of RECTAL VENOUS PLEXUS
- squamous zone- strat sq epi continuous w perianal skin
- anal column (longitudinal folds in anal canal)
- anal sinuses (depression between anal canal)
- ANAL GLANDS (extend into submucosa and muscularis external; BRANCHED, straight TUBULAR mucous
Tunica Muscularis
CIRCULAR muscularis externus (internal anal sphincter)= near anus
external anal sphincter (STRIATED M of pelvic floor for defecations)
Appendix
Tunica Mucosa: SIMPLE COLUMNAR EPI
cialiated cells+ goblet cells
LPM crypts of Lieberkuhn + lymphatic NODULES
LMM
Tunica submucosa: lymphatic NODULES
Tunica muscularis:inner circ+outer long
Tunica Serosa
