Digestive System Flashcards
Oral cavity is lined by mucosa of three different types?
Masticatory mucosa, lining mucosa, specialized mucosa
What is vermillion in lips?
Transitional zone between lining mucosa and skin
What is vermillion lined with?
Thin keratinized stratified squamous, has sensory innervations and capillaries, no hair follicles or glands
What is dorsal side of tongue lined with?
Stratified squamous with patches of keratin
What is ventral side of tongue lined with?
Stratified squamous non keratinized, lingual salivary glands
What is intrinsic muscle in tongue?
Striated muscle, with muscle at right angles of each other, provides flexibility of tongue
What is extrinsic muscle in tongue?
Skeletal muscle, one end attached to bone
What is sulcus terminalis in tongue?
Transitional line that separates tongue in 2/3 anterior and 1/3 posterior
What does anterior 2/3 of tongue contain?
Lingual papillae
What does posterior 1/3 of tongue contain?
Lymphoid follicles called lingual tonsils
What are 4 types of lingual papillae on tongue?
Filiform, Foliate, Fungiform, Circumvallate
Describe Filiform papillae
Located on dorsal surface, projections of CT, keratinized stratified squamous, no taste buds, mechanical function of keeping food on tongue
Describe Fungiform papillae
Mushroom like projections in between filiform papillae, taste buds on apical surface
Describe Foliate papillae
Leaf like on lateral surface of tongue, taste buds located on lateral walls, serous glands empty into clefts
Describe Circumvallate papillae
8-12 located infront of sulcus terminalis, contain most taste buds 250 each, taste buds located on lateral walls, Von Ebners Glands located beneath papillae
Describe Von Ebners Glands
Serous glands that secrete into moat of circumvallate papillae, washes out material stuck in moat, quick perception of taste sensation
Describe taste bud
Cells with taste receptors, taste pore is located at apex
Where can taste buds be found?
Lingual papillae, soft palate, posterior pharynx, posterior epiglottis, glossopalantine fold
What cells do taste buds have?
Supporting cells, sensory cells, basal cells
What are sensory cells in taste buds?
Chemoreceptor cells, most numerous, microvilli on apical surface, tight occluding junctions at apical region, basally synapse with afferent nerves, 10 day turnover
What are supporting cells in taste buds?
Sustentacular cells, microvilli on apical surface, tight occluding junctions at apical region with adjacent cells, 10 day turnover
What are basal cells in taste buds?
Stem cells that replenish sensory and supporting cells
What is soft palate lined with?
Stratified squamous non keratinized, mucus glands and skeletal muscles
What is hard palate line with?
Mucoperiosteum, stratified squamous keratinized and parakeratinized, rugae and palatine glands
How many teeth do humans have?
32
What are the 3 hard tissue types in teeth?
Enamel, denting, cementum with soft tissue pulp
What are the major salivary glands?
Parotid, submandibular, sublingual
What are the minor salivary glands?
Buccal, Lingual, Labial, Palatine
What is main structure of major salivary gland?
Salvion, composed of acinus, intercalated duct, striated duct, excretory duct
What is the acinus?
Function unit blind sac composed of secretory cells
What are the three types of acinus secretory cells?
Serous, Mucous, Mixed
What structure surrounds base of acinus cell?
Connective tissue with nerves and blood vessels
What are acinus cells joined together by?
Junctional complexes
What cell surrounds the acinus cell?
Myoepithelial cell
Where is myoepithelial cell located?
Between basal plasma membrane of acinus cells and basal lamina
What is function of myoepithelial cell?
Long cellular projections contract and squeeze the acinus cell, aids in removal of secretion of saliva that has accumulated in hollow center of acinus, moves it out of duct system
What is merocrine secretion?
Acini mucous, serous, and seromucous secretions secrete products through this
Where are intercalated ducts located?
In between acinus and larger striated duct, prominent in watery serous secreting glands
What is function of intercalated ducts?
Secrete HCO3- ions into acinar products as well as absorb Cl- from acinar products
What is another name for intercalated ducts since they are found in the lobule?
Intralobular ducts
Where is striated duct location?
In between intercalated duct and excretory duct
What is striated duct lined with?
Transitions from simple cuboidal to simple columnar
Why is the striated duct appear striated?
Basal plasma membrane forms infoldings
What does striated duct have enclosed in the membrane infoldings?
Numerous longitudinally arranged mitochondria
What does mitochondria do for striated duct?
Typifies reabsorption of fluids and electrolytes
What is the function of striated duct?
Reabsorption of Na+, secretion of K+ and HCO3-
What is another name for striated duct since found in lobule?
Intralobular duct
What is the excretory duct?
Principle duct, opens in oral cavity
What is excretory duct lined with?
Transitions from simple columnar to pseudostratified columnar to stratified columnar
What is another name for excretory duct since found in lobule
Intralobular duct
Describe parotid gland
Serous gland, secretes proteins and watery secretions, secretions stored in zymogen granules located in apical cytoplasm, numerous rER and ribosomes giving basophilic base, plasma membrane shows basal surface infoldings and basolateral folds
What are two key features in parotid gland that helps with identification?
Facial nerve branches, and intraparotid adipose tissue can be found in adults
Describe submandibular gland
Mixed gland, serous and mucous acini, mucous acini are capped with serous demilunes
Describe sublingual gland
Predominately mucous acini, typically elongated tubules of mucous cells with serous demilunes, called mixed glands with no serous acini secretion, secretions are only mucous
Define mucosa
Epithelium, lamina propria, muscularis mucosae
What does lamina propria typically contain?
CT, vessels, diffused lymphatic tissue, GALT
What is muscularis mucosae?
Thick ring of smooth muscle, allows mucosa to move by itself
What is submucosa?
Thick CT layer that supports mucosa, contains vessels, lymphatics, nerves, contains Meissners plexus (postganglionic neurons of parasympathetic system)
What does submucosa control?
Intestinal gland secretion, movement of water and ions across epithelium
What are the two locations where submucosa contains glands?
Esophagus- Esophageal glands proper
Duodenum- Brunners glands
What is muscularis externa?
Two layers of smooth muscle; inner circular and outer longitudinal, contains parasympathetic nerve plexus Myenteric plexus
What is function of myenteric/auerbachs plexus?
Move perpendicularly to each other to produce PERISTALSIS
Where is serosa found?
Intraperitoneal organs- stomach, spleen, liver, parts of duodenum, small intestine, transverse colon
Where is adventitia found?
Retroperitoneal organs- esophagus, rectum, duodenum, ascending and descending colon
What is serosa?
Mesothelial lining with CT
What is adventitia?
CT with nerves and vessels
What are 4 types of mucosa found in junction zones of GI tract?
Protective, Secretory, Absorptive, Absorptive/Protective
What does absorptive mucosa contain?
Crypts and villi
What genes are responsible for maintaining balance in junctional zones?
Hox genes
What happens when hox genes fail to maintain balance in junctional zones?
Negative changes, malignancies
What are the 4 junctional zones?
Esophageal-gastric zone
Gastro-duodenal zone
Ileo-cecal zone
Recto-anal junction
What change takes place in esophageal-gastric zone?
Stratified squamous of esophagus transitions to simple columnar of stomach
What change takes place in gastro-duodenal zone?
Simple columnar with PITS in stomach transitions to simple columnar with VILLI in duodenum
What change takes place in ileo-cecal zone?
Ileum with only VILLI, transitions to cecum with only CRYPTS
What change takes place in recto-anal zone?
Simple columnar of large intestine, transitions to stratified cuboidal of anus (then transitions to stratified squamous keratinized of anus)
What are pacemaker cells of enteric nervous system?
Interstitial cells of Cajal, ICC
Modulated by parasympathetic nervous system
What does submucosal Meissners plexus control?
Mucosal glands and muscularis mucosae
What does Myenteric/Auerbachs plexus control?
Muscularis externa, responsible for peristalsis movement
What is mucosa of esophagus lined with?
Stratified squamous non keratinized
What does submucosa of esophagus contain?
CT, cardiac glands that secrete neutral mucus, this protects mucosa from regurgitated gastric contents
What is special about muscularis mucosae in esophagus?
It runs longitudinally instead of the normal circularly, it is very thick in esophagus
What does submucosa of esophagus contain?
Dense irregular CT, vessels and lymphatics, Meissners plexus, esophageal glands proper that secrete acidic mucous that lubricates and protects mucosa
What does muscularis externa of esophagus contain?
Smooth muscle layer of inner circular and outer longitudinal, Myenteric plexus between the two layers
What is special about the smooth muscle in muscularis externa of esophagus?
Upper esophagus is striated, middle is striated and smooth, lower is smooth
Does esophagus have serosa or adventitia?
Adventitia until it reaches near intra-abdominal part, then becomes serosa
What is the Z line?
Squamo-columnar junction where esophagus epithelium changes abruptly to stomach epithelium of simple columnar
What happens when Z shifts proximally?
GERD, extreme case is Barrets esophagus, can cause adenocarcinoma
What causes Z line to shift?
Reflux of gastric contents cause damage to esophageal epithelium and cause z line to shift proximally.
What three regions does the stomach have?
Cardiac, Fundic, Pyloric
What does stomach contain that flatten when stomach is full?
Rugae, composed of mucosa and submucosa
What are gastric mucosa invaginations?
Gastric pits or foveolae
What opens at the base of gastric pits?
Gastric glands
What are gastric surface and pits lined with?
Simple columnar epithelium
Fundic glands in fundus extend from?
Bottom of gastric pit to muscularis mucosae
What do surface mucous cells secrete?
Alkaline mucous containing mucin
What do mucous neck cells secrete?
Acidic mucous containing mucin
What do parietal cells secrete?
Intrinsic factor and HCl
What do chief cells secrete?
Pepsinogen and gastric lipase
What do G cells secrete?
Gastrin straight into blood (enteroendocrine cell)
Describe gastrin-histamine complex in parietal cells?
G cells are stimulated, they secrete Gastrin, this activates DNES cells called enterochromaffin like cells ECL, when ECL cells are activated they secrete histamine, the histamine binds with histamine 2 receptors on parietal cells, this causes parietal cell to secrete HCl
What do parietal cells have extensively?
Intracellular canaliculi systems and tubulovesicular membrane systems that contains proton pumps
Explain process of an actively secreting parietal cell?
Intracellular canaliculi systems widen, tubulovesicular membrane system merges with canaliculi system, becomes larger and actively pump protons H+ into lumen;
H2O is split in parietal cell into H+ and hydroxide OH-, H+ is pumped out into the lumen via the H+/K+ pump, while OH- binds with CO2 to form bicarbonate HCO3-, an exchange occurs as HCO3 leaves the parietal cell and enters the capillary, Cl- leaves the capillary and enters parietal cell, then travels to the lumen to meet H+ and forms HCL in lumen
What are enteroendocrine cells also known as?
Neuroendocrine cells, called Diffuse Neuroendocrine System cell, DNES
What are some DNES cells functionally classified as?
Amine Precursor Uptake and Decarboxylation cells, APUD
Where do APUD cells originate from?
Neural crest cells
Where do enteroendocrine cells originate from?
Endoderm
What two secretions does enteroendocrine cells secrete?
Endocrine-into blood circulation, ex. CCK or gastrin
Paracrine- diffuse locally to target cell, ex. Somatostatin
What is an enteroendocrine open cell?
Chemoreceptor, microvilli detect chemical changes in lumen and in response secrete hormones into blood stream
What is an enteroendocrine closed cell?
Paracrine secreting cell, most abundant, not in reach of lumen, hormones secrete paracrine secretions
What is Zollinger Ellison Syndrome?
Also called Gastrinoma, when excessive gastrin secretion occurs and leads to excessive stimulation of parietal cell, excessive HCl secretion, this causes gastric or duodenal ulcers
Where are undifferentiated stem cells located in acinus?
Isthmus region
What cells move upwards from undifferentiated cells?
Surface mucous cells, renewed every 3-5 days
What cells move downwards from undifferentiated cells?
Parietal cells, renewed every 150-200 days
Enteroendocrine and Chief cells, renewed every 60-90 days
Describe cardiac glands
Tubular, mucous secreting and occasional endocrine cells, short pits
Describe pyloric glands
Coiled tubular, deep pits, glands empty into pits, composed of mucous secreting cells, G cells, and parietal cells
What does lamina propria of stomach contain?
Reticular fibers, fibroblasts, smooth muscle, diffused lymphocytes, lymphatic nodules
What does mucularis mucosae of stomach contain?
Inner circular and outer longitudinal smooth muscle
What does submucosa of stomach contain?
Dense CT, blood vessels, Meissners plexus that innervated muscularis mucosae
What does muscularis externa of stomach contain?
Inner oblique, middle circular, outer longitudinal smooth muscle, Myenteric plexus between layers
What does serosa of stomach contain?
Mesothelium with CT
Where does small intestine begin and end?
Gastro-duodenal junction and ends at ileo-cecal junction
What are plicae circulares or valves of Kerckring?
Permanent folds, composed of mucosa and submucosa, increases absorptive surface area of small intestine
What are villi in small intestine?
Projections of mucosa, which consists of epithelium, laminal propria and smooth muscle cells, increases absorptive surface area in small intestine
What does microvilli do for small intestine?
Increase absorptive surface area
Define Lacteal
A central lymphatic vessel in the lamina propria, crucial for absorption of lipids
What are intestinal glands or Crypts of Lieberkuhn?
Tubular glands located in lamina propria, open into intestinal lumen at base of villi, composed of simple columnar continuous with surface cells
What does lamina propria in small intestine contain?
Surrounds intestinal glands, fills core of villi, contains cells of immune system, contains GALT
What are two types of GALT?
Diffuse lymphatic tissue
Nodules of lymphatic tissue
What is diffused lymphatic tissue?
Scattered immune cells throughout lamina propria, ex. Lymphocytes, plasma cells, mast cells
What are nodules of lymphatic tissue?
Cells aggregated into discrete isolated single nodules, nodules can aggregate together too, ex. Peyers Patch
What do enterocytes function in?
Reabsorption of water and electrolytes, digested food, and secretions of enzymes
What junctional complexes do enterocytes hold?
Adhering, desmosomal, and tight junctions at apical surface that form barrier between lumen and intercellular compartment
What do lateral folds do for enterocytes?
Increase lateral surface of cell, enlarge intercellular space during active absorption
What do microvilli do for enterocytes?
Increase surface area for absorption
What do goblet cells provide?
Mucus that is water soluble
Where are paneth cells located?
Base of crypts of leiberkun
What gives paneth cells basophilia in cytoplasm?
High numbers of rER and ribosomes
What gives eosinophilia to paneth cells in apical cytoplasm?
Large secretory granules that contain lysozyme that digest cell walls of bacteria, a-defensins, and zinc
How do paneth cells play a role in regulating normal enteric micro flora?
By phagocytizing bacterial types and protozoa
What do enteroendocrine open cells secrete?
Hormones, ex. Mo cells secrete motilin, I cells secrete CCK
What cells secrete CCK?
I cells
What does MO cells secrete?
Motilin
What do enteroendocrine closed cells secrete?
Paracrine hormones, ex. D cells
What do D cells secrete?
Somatostatin
Where are hormone containing granules located in enteroendocrine cell?
Basal part of cell
What are M cells?
Epithelial cells that overly peyers patches and other lymphatic nodules
Where are M cells located?
Apical surface and have microfolds instead of microvilli
What is special feature of M cells?
Have deep pocket like recess connected to extracellular space
What cells reside in M cell recess?
Dendritic cells, B and T lymphocytes, macrophages
What does apical surface of M cell express?
GP2 receptors for specific macromolecules, like gram negative bacteria
What happens to substances that bind to M cell GP2 receptors?
They are internalized in endocytic vesicles and transported to recess
Why are M cells called Antigen Transporting Cells?
They transport antigens to recess, from apical surface in endocytic vesicles
What do antigens activate in M cells?
GALT for immune response
What are tuft cells?
Chemosensory cells, can detect pathogens too
What are tuft cells characteristic for?
Short tuft of microvilli on apical surface
Are tuft cells apart of immune response?
No
Where are stem cells located?
At base of crypts
What happens to cells that are being replaced by stem cell differentiation?
Cells destined to become goblet or epithelial cells migrate up towards villus, undergo apoptosis, and get sloughed off
When do enterocytes and goblet cells get replenished?
4-6 days
When do endocrine cells replenish?
Every 4 weeks, migrate in both directions
When do paneth cells replenish?
Every 4 weeks, migrate downwards
What are intraepithelial lymphocytes?
Lymphocytes that have migrated to intestinal epithelium and occupy epithelium
What does submucosa of small intestine contain?
Dense CT and Brunners glands in duodenum
What do Brunners Glands secrete?
Both serous and mucous secreting cells, neutralizes acid from stomach which protects small intestine and creates optimal pH for activation of pancreatic enzymes
What does muscularis externa of small intestine contain?
Inner circular and outer longitudinal smooth muscle, Myenteric plexuses between layers
What 2 types of movements does small intestine Myenteric plexus provide?
Segmentation and peristalsis
What is segmentation contraction?
Circular layer only, circulates chyme locally and mixes with digestive juices and moves it to contact with mucosa for absorption
What is peristalsis?
Coordinated movement of inner and outer layer, moves intestinal content distally
What does serosa of small intestine contain?
Mesothelium and small amounts of loose CT
What is function of large intestine?
Reabsorption of electrolytes, water, and elimination of waste
What does mucosa of large intestine contain?
Invaginations to form tubular glands called crypts of leiberkuhn that extend through full thickness of mucosa, composed of goblet cells, no plicae circulares, no villi
What are colonocytes?
Columnar absorptive cells that function in reabsorbing water and electrolytes, located on mucosal surface, numbers decrease distally
Where are goblet cells found in large intestine?
Numerous in crypts, numbers increase towards rectum
What is function of goblet cell in large intestine?
Secrete mucous and facilitate elimination of of semisolid to solid waste
What are tuft cells in large intestine?
Chemosensory cells
What do tuft cells secrete in worm infections in large intestine?
Interleukin 25
When do tuft cells increase in large intestine?
During worm infections
What do tuft cells play a role in, in large intestine?
Initiation of colorectal cancers
What does lamina propria of large intestine contain?
Collagen table, pericryptal fibroblast sheath, GALT, lymphatic vessels
What is collagen table in large intestine lamina propria?
Thick layer of collagen and proteoglycan, between basal lamina and fenestrated capillaries, participates in water and electrolyte transport from intercellular compartments to vascular compartment
What is pericryptal fibroblast sheath in large intestine?
Fibroblast population adjacent to stem cells, cross talk between the two regulates cell division
What is GALT in large intestine?
Well developed lymphocytes and large nodules
Are lymphatic vessels normally present in between crypts?
No, number of vessels increase with inflammation, ex. ulcerative colitis
Why do adenoids and malignancies become very large in large intestine before they enter lymph system?
Lymphatic vessels are not common in large intestine, so the malignancy has to grow large enough to reach a nearby lymph vessel
What does muscularis externa in large intestine contain/
Inner circular and outer longitudinal, condensed into 3 prominent bands called Teniae coli
Does large intestine have serosa or adventitia?
Adventitia since it is retroperitoneal
What does appendix structure consist of?
All four layers of GI present, few crypts, dominant lamina propria with large numbers of lymphatic nodules extending into submucosa, contains absorptive cells, M cells, and goblet cells, covered in serosa
What does mucosa of rectum contain?
Transverse folds called rectal valves, simple columnar, no villi, deep simple tubular intestinal glands, large number of goblet cells
What is anal canal divided into and where are parts derived from?
Upper 2/3 is derived from endoderm, lower 1/3 is derived from surface ectoderm
What is the junction called between upper 2/3 and lower 1/3 of anal canal?
Pectinate or Dentate line
What type of columns are present in mucosa above pectinate line?
Anal columns called Columns of Morgangi
What is present at inferior ends of Columns of Morgangi in anal canal?
Anal valves, with anal sinuses slightly above them that contain mucous secreting glands
What does submucosa of anal canal contain?
Deep branched tubular glands called anal glands, circumanal glands that are apocrine sweat glands, and venous plexuses
What does muscularis externa of anal canal contain?
Inner circular and outer longitudinal, in the middle third of anal canal- the inner circular layer forms the internal anal sphincter (smooth muscle)
What is external anal sphincter formed by?
Skeletal muscle
What lines the upper 1/3 or colorectal zone?
Simple columnar, derived from hind gut endoderm
What lines the middle 1/3 or anal transition zone?
Stratified cuboidal with no muscularis mucosae, derived from hind gut endoderm
What lines the lower 1/3 or squamous zone?
Stratified squamous keratinized (after hiltons white line), derived from surface ectoderm
What is junction called at squamous zone when stratified squamous becomes keratinized?
Hiltons white line
What does Hiltons White line demarcate?
Junction of internal and external anal sphincter
What does liver function in?
Glucose metabolism, protein metabolism, lipid metabolism, storage of vitamin A and D and iron, detoxification, removal of damaged RBC, bile production, eliminates waste products
What does Hepatic portal vein bring to liver?
Nutrients and toxic material absorbed, blood cells and breakdown from spleen, endocrine secretions from pancreas, deoxygenated blood that empties into sinusoids
What does Hepatic artery bring into liver?
Oxygenated blood that empties into sinusoids
Why are liver sinusoids never fully exposed to oxygenated blood?
Because the hepatic portal vein brings in deoxygenated blood, hepatic artery brings in oxygenated blood, this forms a mixture of the two, never allowing sinusoids to be fully exposed to oxygenated blood only
What are liver sinusoids remnants of?
Fetal vitelline veins
What function do liver sinusoids hold?
Provide exchange of substances between blood and hepatocytes
Where do liver sinusoids drain?
Drain into central vein
What is order of draining?
Sinusoid-Central vein-Sublobular veins-Hepatic veins-IVC
What does liver parenchyma consist of?
Plates of hepatocytes, separated by sinusoids
What does connective tissue stroma of liver consist of?
Glissons capsule, blood vessels, nerves, lymphatics, bile ducts transverse in CT
What are sinusoids?
Vascular channels
What is Space of Disse?
Space between hepatocytes and sinusoidal endothelium
What is classic lobule?
Hexagonal mass of tissue, with central vein in middle and 6 adjacent portal triads
What is Space of Mall?
Space between hepatocytes and portal triad, site where lymph originates in liver
Where does lymph originate in liver?
Space of Mall
What is portal lobule?
Parenchyma is divided into interlocking triangles, consists of portal triad in the center and central veins at each end of 3 corners
Explain flow of bile
Bile produced by hepatocytes enters membrane bound bile canaliculi between them and flows within hepatocyte plate towards bile duct in portal triad, moves opposite of blood flow
What is liver acinus?
Diamond shaped, contains 2 central veins as long axis, and 2 portal triads as short axis
What is the line connecting the two portal triads in liver acinus?
What does it provide?
Along this line runs the hepatic artery and portal vein that deliver blood into sinusoids
Best correlation between blood perfusion, metabolic activity, and liver pathology
Describe Zone 1 of liver acinus
Closest to vessels, higher metabolic rate, large glycogen storage, last to die and first to regenerate. However, toxins in blood and bile stasis would effect zone 1 first
Describe Zone 3 of liver acinus
Closer to central vein, last to receive oxygen or nutrition, cells get damaged without adequate nutrition, first to show ischemic necrosis during reduced perfusion, first to show fat accumulation, first to be effected in heart failure with inadequate blood to liver. However, last to respond to blood toxins or bile stasis
Purpose of central lobule?
Drains blood from hepatic artery and portal vein to the central vein
Purpose of portal lobule?
Drains bile from hepatocytes to the bile duct
Purpose of Liver acinus?
Supplies oxygenated blood to hepatocytes
What does portal vein provide?
Venous blood to sinusoids
What does hepatic artery provide?
Arterial blood to sinusoids
What does central vein receive?
Blood from hepatic sinusoids
Sinusoids are lined with what?
Endothelial cells and Kupffer cells
Endothelial cells have wide open fenestrate, and?
No diaphragm, discontinuous with large gaps between cells
What are endothelial cells supported by?
Discontinuous basal lamina
What is space of Disse?
Space between hepatocytes and endothelial cells, and kupffer cells
What is important about space of disse?
Site of exchange of materials between blood and hepatocytes
What does space of disse hold in adults?
Plasma
What does space of disse hold in fetus?
Islands of blood forming cells
What project into space of hepatocytes?
Small microvilli
Where is Stellate cell/ Ito cell found?
In space of disse
What is function of Ito cell?
Storage of vitamin A as retinyl esters in cytoplasmic lipid droplets
What happens to Ito cells in liver cirrhosis and chronic inflammation?
Loose Vitamin A storage and differentiate into myofibroblasts, they then deposit type I and III collagen in perisinusoidal space which causes liver fibrosis
What happens during recovery of liver injury?
Stellate/ Ito cells remodel extracellular matrix
Describe how Ito cells cause portal hypertension?
Stellate/ Ito cells secrete GAGs and type I and III collagen, this leads to loss of sinusoidal fenestrations and may even turn into capillaries. Multiplied Ito cells contract and increase vascular resistance within sinusoid, causing portal hypertension
What are Kupffer cells?
Derived from monocytes, form part of sinusoidal lining but do not form junctions with endothelial cells, involved in breakdown of RBCs, increase in number after splenectomy
Why do Kupffer cells show yellow pigmentation?
They show hemosiderin, resulting from destruction of RBC
What are pit cells?
Liver specific natural killer cells, belong to group of sinusoidal cells
Why are pit cells known as large granular lymphocytes?
They are lymphoid cells containing specific granules
Where do majority of hepatocyte cells live?
Quiescent in G0 phase
Liver has good capacity for regeneration because?
They undergo mitosis when stimulated, ex. after partial hepatectomy, hepatocytes reenter cell cycle by going from G0 phase to G1 phase
What do hepatocytes have numerous of?
Mitochondria, small golgi, rER and ribosomes, peroxisomes and lysosomes
Cell surface specializations of hepatocytes include?
Sinusoidal- that are covered in microvilli
Basolateral- that have tight junctions, desmosomes, and gap junctions
Bile canaliculi- small tubules between adjacent cells through which bile flows
What is function of peroxisomes?
Breakdown of hydrogen peroxide produced in many general cytoplasmic activities using the enzyme CATALASE
What is role of alcohol dehydrogenase?
1/2 of alcohol ingested is converted to acetaldehyde
What are lysosomes involved in?
Degradation of foreign material and unwanted cytoplasmic organelles, by autophagy
What is biliary tree?
System of conduits of increasing diameter, carry bile from hepatocytes to gallbladder and then to intestine
What does biliary tree start with?
Bile canaliculi, small passages formed by apposed grooves on lateral surface of neighboring hepatocytes that contain short microvilli, sealed from the rest of intercellular compartment by junctional complexes
What does the gallbladder function in?
Concentration and storage of bile
What does gallbladder release bile in response to?
CCK Cholecystokinin
What does mucosa contain in gallbladder?
Epithelium and lamina propria, folds when gallbladder is empty
What does epithelium of gallbladder contain?
Lined with simple columnar called cholangiocytes, well developed microvilli, apical junctional complexes, apical and basal concentrations of mitochondria, lateral folds
What are Cholangiocytes?
Simple columnar cells found in gallbladder, specialized for water reabsorption
What do epithelial cells of gallbladder actively transport?
Na+ and Cl- from cytoplasm to intercellular space, lateral movement of NaCl forces water to move from cytoplasm to intercellular space, intercellular space widens and water moves from intercellular space to the underlying fenestrated capillaries of lamina propria
What does lamina propria in gallbladder contain?
Fenestrated capillaries, many lymphocytes and plasma cells
What pockets does mucosa form in gallbladder?
Deep diverticula, called Rokitansky-Aschoff sinuses
How are Rokitansky-Aschoff sinuses formed?
Growth and herniation of epithelium, may extend through muscularis externa
What is negative factor of Rokitansky-Aschoff sinuses?
Bacteria can accumulate and cause risk factor for gallstones
What does muscularis of gallbladder contain?
Bundles of smooth muscle
What induces muscle contraction of muscularis in gallbladder?
CCK cholecystokinin, released by enteroendocrine cells of small intestine, release of CCK is stimulated by the presence of ingested fat in small intestine
What is pancreas gland and what does it produce?
Mixed exocrine-endocrine glands, produces both digestive enzymes and hormones
What does exocrine of pancreas do?
Serous gland, synthesizes and secretes into duodenum enzymes needed for digestion, ex. proteases, lipase, amylase, bicarbonate
What does exocrine gland surround in pancreas?
Islets of Langerhans
What does endocrine of pancreas do?
Synthesizes and secretes into blood, insulin, glucagon, and somatostatin, regulates glucose metabolism
What do exocrine serous cells of pancreas exhibit?
Zymogen granules
What are exocrine acinus drained by?
Intercalated ducts, no striated ducts, secrete 1.5L a day
What are intercalated ducts of pancreas?
Initial cells of duct extend into lumen of acinus, these cells are called CENTROACINAR cells, unique to pancreas
What are CENTROACINAR cells?
Cells of pancreas duct that extend into lumen of acinus, lack zymogen granules, stain lightly with eosin
What do CENTROACINAR cells secrete?
Fluid rich in Na and bicarbonate, neutralizes chyme which creates optimal pH for enzymes
What do intercalated ducts merge to form?
Larger interlobular ducts, these join with each other to form main pancreatic duct
