10843318
Description
Flashcards by Brianne Schmiegelow, updated more than 1 year ago
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Created by Brianne Schmiegelow
over 6 years ago
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| Question | Answer |
| What are the primary and secondary functions of bone and cartilage? | 1': support and locomotion/movement 2': protection, mineral storage, and hemopoiesis |
| What are bone and cartilage derived from? Why are they strong? | Primitive mesenchymal cells Properties of ground substance and extracellular fibers they have |
| Formation of cartilage | Stellate mesenchymal cells differentiate into rounded chondroblasts These grow and synthesize ground substance and extracellular matrix, trapping themselves in lacunae Further mitotic divisions produce clusters of mature chondrocytes (aka isogenous groups) separated by extracellular matrix |
| What is perichondrium? | Peripheral zone of dense CT that surrounds cartilage Contains fibroblasts, collagen, and immature chondroblasts |
| What is interstitial growth? | Type of cartilage growth New cartilage forms within mass and chondrocytes retain the ability to divide |
| What is appositional growth? | Type of cartilage growth New cartilage forms at the surface of pre-existing cartilage MORE COMMON New chondrocytes from mesenchymal cells of inner perichondrium differentiate first into chondroblasts More mature chondrocytes present at center of cartilage mass with younger cells at the periphery |
| Characteristics of cartilage | Avascular CT (most lack blood vessels) Exchange of metabolites occurs via diffusion through ground substance (limits thickness of mature cartilage, so thick cartilage contains BVs in 2' cartilage canals) Has collagenous ground substance |
| What makes up the extracellular matrix of cartilage? | Amorphous ground substance containing collagen and 60-80% H2O Bound to proteoglycans that account for its flexibility and incompressibility GAG's include hyaluronic acid (non-sulfated), chondroitin sulfate, and heparan sulfate Most common glycoprotein is chondronectin |
| Characteristics of hyaline cartilage | Has small aggregates of chondrocytes in amorphous matrix of ground substance reinforced with Type II collagen fibers Precursor for bone in most of skeleton Found in articular surfaces, growth plates, nasal septum, costal cartilage (ribs), tracheal and bronchial rings |
| Characteristics and location of fibrocartilage | Consists of alternating layers of hyaline cartilage and dense CT (contains Type I AND Type II collagen) Lacks perichondrium Found in intervertebral discs, TMJ, shoulder, etc. |
| Characteristics and location of elastic cartilage | Similar to hyaline cartilage (contains Type II collagen) with addition of large amounts of elastic fibers in the ECM Found in external ear, auditory and Eustacian canals, epiglottis, and larynx |
| Process of cartilage repair | LIMITED because repair requires blood flow Results in production of dense CT (FIBROSIS) Invasion of site by BVs frequently results in death of chondrocytes and formation of bone Tendency for all hyaline cartilage to calcify with age via deposition of calcium phosphate crystals within matrix (eventually replaced by bone) |
| What is woven bone? | Immature form of bone Characterized by random orientation of collagen fibers |
| What is lamellar bone? | Mature bone form Contains concentric layers (circumferential lamellae) with parallel collagen fibers Can be dense and compact (e.g. cortex of long bones) or cancellous AKA spongy (e.g. ends of bones) |
| What are trabeculae? | AKA spicules Thin branches of bone surrounded by open spaces (marrow cavity) Makes up cancellous (spongy) lamellar bone |
| What is the diaphysis? | Shaft of long bone Composed of dense, compact bone in cortex and spongy, cancellous bone in medullary cavity (where marrow is found) Contains red (hematopoietic) and yellow (fatty) marrow |
| What is the epiphyses? | Ends of long bones Composed of spongy, cancellous bone covered with hyaline articular artilage |
| What is the metaphysis? | Flared region of long bone between the epiphysis and diaphysis Contains epiphyseal plate ("physis") of long bones |
| What is the periosteum? | Layer of fibrous CT that covers the external surface of bone Contains fibroblasts and osteoprogenitor cells |
| What is endosteum? | Lining of internal marrow cavity of bone |
| What are Sharpey's fibers? | Parallel bundles of collagen fibers that extend from the periosteum or muscle tendon around bones and insert into the superficial layer of the bone itself Provide anchorage and support |
| What are osteoprogenitor cells? | Resting mesenchymal cells that reside in the periosteum and endosteum Can differentiate into osteoblasts and osteocytes |
| What are osteoblasts? | Roughly polygonal mesenchymal cells derived from osteoprogenitor cells Very basophilic due to synthesis of large amounts of protein and proteoglycans Responsible for synthesis of osteoid (ECM and collagen) that is later mineralized to form new bone Responsible for calcification of matrix via secretion of matrix vesicles Mature into osteocytes within lacunae after matrix mineralizes |
| What are matrix vesicles? | Vesicles secreted by osteoblasts Contain alkaline phosphatase Bud off osteoblasts into matrix causing precipitation of mineral salts (e.g. Ca and PO4) |
| What are osteocytes? | Mature "bone cells" |
| What are osteoclasts? | Large multinucleate cells derived from monocyte-macrophage lineage Phagocytic cells Actively involved in resorption and remodeling of bone Usually found on endosteal/periosteal surface in depressions called Howship's lacunae (aka resorption bays) Function in Ca homeostasis by producing organic acids and lysozymes that digest bone |
| What is the ruffled border? | Modified, folded plasma membrane that contains microvilli-like structures Found on osteoclasts Secretes organic acids and lysozymes into ECS to digest bone |
| What is parathormone? | AKA parathyroid hormone Secreted by parathyroid gland Stimulates osteoclast activity => bone resorption Increases blood Ca levels and decreases renal excretion by the kidneys |
| What is calcitonin? | Hormone secreted by the thyroid gland Stimulates osteoblast activity, inhibits osteoclasts => bone deposition Decreases blood Ca levels |
| What is somatotropin? | AKA pituitary growth hormone Stimulates growth (especially epiphyseal cartilage and bone) Decreases blood Ca Oversecretion can lead to gigantism (AKA acromegaly) Undersecretion leads to pituitary dwarfism |
| What makes up mature, compact bone? | ~70% inorganic salts and 30% organic matrix |
| What makes up the organic matrix of bone? | >90% Type I collagen synthesized by osteoblasts Hyaluronic acid and chondroitin sulfate (GAG's) Osteocalcin, osteonectin, and sialoproteins |
| What do the non-collagenous organic molecules in bone do? | Osteocalcin: binds intracellular Ca during mineralization Osteonectin: bridges/binds collagen and minerals Sialoproteins: rich in sialic acid; concentrated from plasma |
| What is the mineralized component of bone? | Formed by inorganic salts Primarily Ca and P in form of hydroxyapatite crystals Ca10(PO4)6(OH)2 ALSO has affinity for heavy metals (e.g. Pb, Hg) and radioactive isotopes; why lead is so dangerous to growing kids |
| What are Haversian systems? | AKA osteons Remodeled bone in compact bone (removal of existing bone by osteoclasts and redeposition of new bone by osteoblasts) About 200 micron diameter (same as size of osteoclast) |
| What is the cement line? | Outer margin of an osteon |
| What is the ultrastructure of compact bone? | Concentric bony lamellae laid down by successive layers of osteoblasts, trapping themselves in lacunae in osteoid matrix Osteoblasts then mature into osteocytes that are connected by minute canals (canaliculi) containing cytoplasmic extensions that allow them to communicate with each other via gap junctions Within the center of each osteon is the Haversian canal that contains BVs and nerves |
| What are Volkmann's canals? | Transverse canals that connect the longitudinal Haversian canals in compact bone |
| How does exchange of waste and nutrients occur in compact bone? | Via Haversian vessels that are oriented parallel to the long axis of bone |
| What are interstitial systems? | Inactive Haversian systems in compact bone |
| What are circumferential lamellae? | Organization of the outer periphery of cortical bone |
| What controls bone growth? | Growth hormone, thyroid hormone, and sex hormones |
| What is endochondral ossification? | Replacement of cartilage precursor by bone Resulting woven bone is extensively remodeled by resorption and appositional growth to lead to lamellar bone (e.g. long bones, vertebrae, pelvis, and base of skull) Most common bone growth pathway |
| What is intramembranous ossification? | Direct replacement of mesenchyme by bone with NO cartilage precursor Mesenchymal cells differentiate into osteoblasts, produce osteoid, and later mineralize into bone (e.g. vault of skull) Much less common than endochondral oss. |
| Process of endochondral ossification | 1. Precursor of long bone formed of hyaline cartilage 2. Osteoprogenitor cells and osteoblasts secrete osteoid which mineralizes to form periosteal cuff 3. Calcification of cartilage matrix inhibits diffusion of nutrients, leading to the death of chondrocytes and the spread of osteoblasts 4. Osteoprogenitor cells from periosteum migrate into medulla along with growing blood vessels 5. Mineralization spreads across cartilage matrix 6. Thin region of unmineralized bone remains between sites of ossification (epiphyseal plate) |
| Where are the centers of ossification in endochondral oss.? | Primary: mid-diaphysis Secondary (2): epiphyses |
| What is closure of epiphysis? | Complete ossification of endochondral oss. bone that occurs at maturity Results from changes in hormones that decrease cartilage proliferation and the replacing of cartilage plate replaced by bone Limits body size and length of long bones After closure, the growth plate persists as an epiphyseal line in metaphysis and is visible on X-rays |
| What is the last long bone to close in humans? | FEMUR Occurs ~18-20 |
| What are the zones in the epiphyseal growth plate? | Zone of reserve cartilage: hyaline cartilage with clusters of chondrocytes (no cell proliferation) Zone of proliferation: successive mitotic division of chondrocytes => columns of chondrocytes Zone of maturation: division ceases; chondrocytes increasing in size Zone of hypertrophy (and calcification): chondrocyes greatly enlarge, contain large amounts of glycogen, become vacuolated and calcify Zone of (cartilage) degeneration: capillaries of marrow cavity grow from diaphysis into growth plate; chondrocytes degenerate; lacunae invaded by osteogenic cells Zone of ossification: BVs from marrow cavity grow into cartilage mass; osteogenic cells differentiate into osteoblasts, congregate on spicules of calcified cartilage matrix to form bony trabeculae |
| Process of intramembranous ossification | 1. Mesenchymal cells differentiate directly into osteoblasts then begin synthesizing osteoid at multiple sites (centers of ossification) within membrane 2. Mineralization follows with subsequent fusion of adjacent centers of ossification 3. Osteoblasts trapped within lacunae of osteoid and become osteocytes 4. Osteoprogenitor cells at periphery continue to divide and provide replacements 5. Bone produced is woven bone that is later remodeled by osteoclasts and osteoblasts to form compact or spongy bone |
| What are the different types of fractures of bone? | Simple (closed): no break in skin Compound (open): damage to skin exposing bone Comminuted: bone broken in several pieces |
| What is the process of bone repair? | 1. Immediately after fracture, blood fills fracture site, forming a hematoma, and the inflammatory response develops 2. In acute phase (first few days) neutrophils first to arrive and infiltrate hematoma, then macrophages (both phagocytic) to clean up site of injury 3. After 1 week, fibroblasts and caps proliferate and grow into site 4. This forms granulation tissue (vascular collagenous tissue) which becomes progressively more fibrous in chronic phase and forms fibrous granulation tissue 5. Mesenchymal cells differentiate into chondroblasts and secrete matrix to replace gran. tissue with hyaline cartilage (called provisional callous) 6. Osteoprog. cells and osteoblasts from end/peri-osteum at edge of wound grow inward and produce meshwork of woven bone within provisional callous (deposit Ca salts in collagen matrix) 7. This transforms into a bony callous that helps stabilize and bind fracture together 8. Fracture site completely bridged by woven bone (called bony union) 9. Bony callous progressively remodeled into mature lamellar bone 10. Process takes 6-12 weeks |
| When do you need to "set" a fracture? | BEFORE provisional callous transforms into bony callous |
| What is a synovial joint? | Joint characterized by extensive movement AKA diarthroses Surrounded by CT capsule (joint capsule) Lined by thin, discontinuous layer of cells (synovium) that secretes synovial fluid to bath the articular surface NO basement membrane (so not a true epithelium) Made up of 4 layers of synovial cells of mesenchymal origin Have A & B type cells |
| Types of synovial cells | Type A: resemble macrophages Type B: resemble fibroblasts |
| What are nonsynovial joints? | Joints with limited movement that are joined by dense CT and lack articular surface Includes syndesmosis, synchondrosis, and symphysis |
| What is a syndesmosis? | Dense fibrous tissue between bones In skull, progressively replaced by bone to become synostosis (aka "sutures") |
| What is a synchondrosis? | AKA 1' cartilage joint Contains single layer of hyaline cartilage Unites first rib with sternum (only one in human adult) |
| What is a symphysis? | AKA 2' cartilage joint Contains two hyaline cartilage surfaces connected by a fibrocartilage plate |
| What are intervertebral joints? | Special type of symphysis Contain intervertebral discs (evolutionarily derived from notochord in chordates) Formed of concentric layers of fibrocartilage Forms annulus fibrosus around central core of viscous ground substance (nucleus pulposus) |
| What causes a herniated disc? | Damage to annulus fibrosus of intervertebral disc that causes the nucleus pulposus to herniate Can cause sciatica |
| What is arthritis? | Inflammation of joints |
| What is osteoarthritis? | Progressive degeneration and loss of articular cartilage Leads to eburnation, pitting, and erosion that leas to pain, swelling, and thickening of the joint capsule |
| What are osteophytes? | AKA bone spurs Production of irregular new bone at edges of articular surfaces Limits range of motion |
| What is ankylosis? | Bony fusion of joint with loss of mobility Result of progressive build-up of osteophytes, osteoarthritis, and/or trauma |
| What is rheumatoid arthritis? | Local, autoimmune reaction in joints Causes pain/damage to articular cartilage and thickening/inflammation of synovial membrane |
| What is pannus? | Replacement of articular cartilage with fibrovascular tissue Result of rheumatoid arthritis |
| What is gout? | Deposit of urates and uric acid crystals in joints (esp. fingers and toes) Extremely painful, assoc. with consumption of large quantities of red wine/meat Also caused by asparagus, broccoli, cauliflower, and brussel sprouts All represent new plant growth, high in protein and [N] ALSO some diuretics used to treat hypertension |
| What is rickets? | Disease in which bone matrix doesn't calcify normally in children during growth Causes soft, deformed bones that can be permanent Due to insufficient dietary Ca or Vit D Called osteomalacia in adults |
| What is osteoporosis? How do we treat it? | Loss of bone mass caused by an imbalance in resorption by osteoclasts vs deposition by osteoblasts Common in post-menopausal women (possible due to decrease in estrogen levels) Treat with oral Ca supplem. and Vit D for increased Ca absorption Chondroitin, glucosamine, and gelatin also helpful Newer meds (e.g. Fosamax) bind phosphate in GI tract to minimize absorption (side effects include mandibular necrosis) |
| What is scurvy? | Disease caused by deficiency of Vit C that is necessary for synthesis of collagen Results in bone matrix not calcifying and weakening of collagen in ligaments (esp. periodontal ligament) Causes breakdown of scars/old wounds which then break open and bleed Treat with fruits and veggies high in VitC |
| What is dense lymphoid tissue? | LT organized into discreet structures or organs E.g. spleen, lymph nodes, thymus, tonsil |
| What is diffuse lymphoid tissue? | LT located throughout the body and assoc. with mucous membranes |
| What is MALT? | Lymphoid tissue common in respiratory and digestive tracts |
| What is 1' lymphoid tissue? | Lymphoid tissue where b- and t-cells acquire surface receptors Bone marrow (b-cells) & thymus (t-cells) |
| What is 2' lymphoid tissue? | Where mature b- and t-cells migrate to |
| Lymphomas vs. leukemias | Both malignant tumors of immune system Solid organs: lymphomas Involve blood: leukemias |
| Characteristics of lymphatic vessels | Network of blind-ended vessels in CT Provide a route which allows cells and large molecules in ECS to re-enter bloodstream Assist circulation of lymphocytes and concentrate antigens for elimination within lymph nodes |
| What are lymph nodes? | Encapsulated aggregates of lymphocytes and lymphoid tissue distributed throughout the body Type of dense lymphatic tissue Arranged in chains or clusters along vessels of lymphatic origin e.g. submandibular, cervical, axillary, femoral, popliteal, hilar |
| What are the four functions of lymph nodes? | Non-specific filtering of particulate matter and microorganisms from lymph Interaction of circulating lymphocytes with antigens in lymph Aggregation, activation, and proliferation of b-cells with subsequent antibody production Aggregation/proliferation of t-cells and induction of cytotoxic immunity |
| What is a lymphoid cell? | Lymphocytes of all types found in lymph nodes Derived from bone marrow and enter node via bloodstream |
| What is an immune accessory cell? | Antigen-presenting cells (macrophages, b/t-cells) that originate in the bone marrow and are found in the lymph nodes Types: Follicular dendritic cells: macrophage at periphery of germinal centers Tingible body macrophage: cell with phagocytic vesicles that stain variably; found in germinal centers |
| What are stromal cells? | Fibroblasts and reticular cells (fibroblast-like cells with phagocytic capability) in lymph nodes Along with extracellular products (collagen and reticular fibers), form CT skeleton of lymph nodes |
| Morphology of lymph nodes | Outer fibrous capsule (dense, irregular CT) Dense, outer, cellular cortex (b/t-cells and plasma cells) Less cellular inner medulla Has extensions of cortex into medulla called MEDULLARY CORDS Has very thin, collagenous trabeculae throughout cortex and medulla Blood vessels enter and leave at hilus |
| What are medullary sinuses? | Broad lymphatic channels in the lymph nodes Separate the cortex and the medulla |
| What is the process of diapedesis? | How b/t cells leave bloodstream and enter lymph node Facilitated by complementary adhesion molecules (ADDRESSINS) present on both endothelial cells and lymphocytes Cells migrate across walls of specialized post-capillary venules (HIGH ENDOTHELIAL VENULES) that are lined by cuboidal/columnar endothelium |
| Where do you find high endothelial venules? | Deep, inner cortex of lymph node at the corticomedullary junction (AKA paracortical zone) |
| What is the cortical sinus? | AKA subcapsular sinus Space beneath capsule of lymph node where numerous AFFERENT lymph vessels drain into Endothelium on side adjacent to capsule is CONTINUOUS (prevents leakage) but DISCONTINUOUS on side adjacent to parencyma Not open spaces like blood sinuses, but filled with reticular fibers and macrophage processes |
| What are other names for cortical sinuses? | trabecular and peritrabecular |
| What are medullary sinuses? | Broad, lymphatic channels in inner, less cellular medulla of lymph nodes Contain lymphocytes, plasma cells, and macrophages Converges on hilus where lymph drains via a single EFFERENT lymph vessel Lymph eventually returns to blood stream via thoracic duct or right lymphatic duct Drainage to regional lymph nodes is important in metastasis of tumor cells (esp in thorax) |
| What are lymphoid follicles? | AKA lymphatic nodules AKA 1' follicles Densely packed, highly cellular areas within cortex of lymph nodes Sites of b-cell proliferation, 2' hemopoiesis Contain lymphoblasts, macrophages, and immature b/t-cells |
| What are 2' lymphoid follicles? | LF's that contain germinal centers (paler, less dense areas) that indicate the lymph node is responding to antigens This occurs via clonal expansion (increased antibody production) |
| What causes swollen lymph nodes? | Proliferation of lymphocytes in lymphoid follicles |
| What is the mantle zone? | Region of antigen presentation in 2' lymphoid follicles Darker staining rim surrounding germinal center |
| Characteristics of the thymus | Lobular, lymphatic organ located in the mediastinum Similar appearance to lymph nodes but NO lymphoid follicles and medulla lacks medullary cords/sinuses Has thin capsule of dense, irregular CT Slender interlobular septa (AKA trabeculae) divide thymus into lobules Highly cellular cortex packed with lymphocytes (mostly t-cells and macrophages) NO 2' follicles, so limited local clonal expansion of t-cells Has less cellular, central medulla that contains b-cells, plasma cells, and macrophages Inner surface of capsule has continuous epithelium to isolate thymus NO afferent lymph vessels, only EFFERENT (b/c t-cells not fully differentiated) |
| From where is the thymus embryologically derived? | From epithelial outgrowth of 3rd pharyngeal pouch Important hematopoietic organ during fetal development!!! |
| Four functions of the thymus | Production of mature, immunocompetent Th and Tc cells Clonal proliferation of Tc cells Clonal deletion of self-antibodies (development of immunologic self-tolerance) Secretion of hormones regulating t-cell development and maturation |
| As t-cells mature, they express: | Antigen-specific t-cell receptors CD (cluster of differentiation) surface markers Class I and II HLA (human leukocyte antigen) surface markers |
| What are nurse cells? | Epithelial cells within the thymus that provide nurse function and structural support Secrete thymotaxin, thymosin, and thymopoietin hormones that attract, regulate, and promote t-cell proliferation/differentiation into Tc, Ts, & Th cells |
| What are Hassal's corpuscles? | AKA thymic corpuscles Eosinophilic, lamellated structures within both medulla and cortex of the thymus Represent degenerate reticular and epithelial nurse cells |
| What happens to the thymus at puberty? | Degenerates (vestigial in adults) Undergoes fatty infiltration and lymphatic depletion (AKA thymic involution) |
| What is the blood-thymus barrier? | CT sheath around endothelium and basement membrane of thymic blood vessels that forms a continuous antigenic barrier Isolates the thymus from the immune system Consists of epithelioreticular cells, reticular fibers, fibroblasts, macrophages, plasma cells |
| What is the largest lymphoid organ in the body? | Spleen |
| What are the functions of the spleen? | B/t cell replication, manufacturing of antibodies, antigen removal Removes particulate matter and aged/defective RBCs from circulation via phagocytosis Recycles iron from hemoglobin Hemopoiesis in fetus |
| What happens if the spleen is removed? | Function taken over by liver and bone marrow |
| Histology of spleen | Dense, fibroelastic outer capsule with smooth muscle cells that is important in splenic contraction (some species like dogs/cats to increase BVs in limbs) and acts as a reservoir for RBCs Large, thick bands of dense CT trabeculae that extend into the body (can have BVs within) NO cortex and medulla Bulk composed of red pulp with white pulp scattered within |
| What is red pulp? | Spongy matrix in spleen Pulp cords (cords of Bilroth) and sinusoids found within Sinusoids have blood, pulp cords have macrophages (phagocytize senescent RBC) and lymphocytes |
| What supports pulp cords in red pulp in spleen? | CT skeleton of reticular cells and reticular fibers |
| What is white pulp? | Discreet nodules within red pump of spleen Contain large numbers of WBCs Functions as site of antigen presentation and phagocytosis Contains lots of macrophages, plasma cells, and t-helper cells |
| What are the areas of white pulp? | Follicular areas Germinal centers (if previously exposed to antigen): contain primary b-cells Central artery: in middle Mantle zone: thin, basophilic area around central artery Marginal zone: paler zone around the mantle zone |
| What are splenic nodules? | Enlarged germinal centers visible to the naked eye AKA area of white pulp that has a germinal center |
| What are periarteriolar lymphatic sheaths (PALS)? | Areas where central arteries of white pulp of spleen surrounded by t-cells rather than b-cells Lack germinal centers (bc minimal t-cell proliferation) Less well-developed in humans and require immunohistochemical staining to make positive ID Term often used interchangeable with primary follicles in white pulp (even though it really shouldn't be) |
| Open circulation model of spleen | Branches of SPLENIC arteries enter white pulp within trabeculae via TRABECULAR arteries, then branch and form CENTRAL arteries to white pulp CENTRALs continue into red pulp, branch into perpendicular PENICILLAR arteries, branch into ARTERIOLES, and terminate in 2-3 SHEATHED CAPILLARIES (blind-ending capillaries that lack endothelial lining and are surrounded by macrophages) Blood cells leave caps via diapedesis and enter sinuses in red pulp Blood drains out via TRABECULAR veins and empties into SPLENIC veins |
| How does splenic filtration occur within circulation? | CUFF (non-continuous perivascular sheath) of sheathed capillaries Act as part of filtering mechanism and are active in phagocytosis |
| What are stave cells? | Endothelial cells that line the sinusoids in the spleen Slits between these cells allow free passage of blood cells |
| What is Waldeyer's ring? | Collective term for palatal, lingual, and pharyngeal tonsils Forms ring of immunologic protection of GI and respiratory tracts |
| What are palatine tonsils? | Paired structures located at the junction of oral and pharyngeal cavities within tonsillar crypts between anterior and posterior tonsilar pillars (AKA palatoglossal and palatopharyngeal arches) Unencapsulated but supported by cup-shaped, collagenous hemicapsule at the base NO cortex/medulla Lymphoid follicles scattered throughout the parenchyma (may include germinal centers) |
| What are lingual tonsils? | Tonsils present at base of tongue and pharyngeal tonsils (AKA adenoids) in nasopharynx Associated with Eustacian tubes |
| What is NALT? | Nasal-associated lymphoid tissue Collective term for the palatal and pharyngeal tonsils |
| What covers the luminal surface of palatine and lingual tonsils? | Stratified squamous non-keratinized epithelium Invades the tonsil, forming blind-ended TONSILAR CRYPTS |
| What is the appendix? | Blind-ended sac of vestigial cecum; DIFFUSE lymphoid tissue Atrophies in adults Contains mostly b-cells Important digestive organ in herbivores used for bacterial fermentation |
| What is mucosa-associated lymphoid tissue? | AKA MALT (in gut = GALT; in resp. tract = BALT; in pharynx = NALT) Diffuse, unencapsulated lymphoid aggregates associated with mucosal surfaces Located in subepithelial CT of lamina propria Contains mainly B-cells Produces primary IgA (AKA secretory IgA) May contain germinal centers |
| What is the function of MALT? | Samples antigenic material, produces lymphoblasts, secretes antibodies Contains specialized M-cells (AKA squamoid enterocytes) in surface epithelium with microfolds on surface that are responsible for antigen sampling and transfer from the gut lumen into lymphoid follicles |
| When is MALT formed? When is it at max distribution? | Formed during fetal development Distribution max in childhood and progressively atrophies with age |
| What are Peyer's patches? | Special type of MALT scattered throughout small intestine MOST common in ileum, and LEAST common in duodenum Project into lumen of the gut in DOME AREAS with cuboidal mucosa Also contain M-cells (similar to MALT) Lymphoid aggregates contain lots of b and t cells DON'T produce lots of IgA Frequent germinal centers associated with foci of b-cells |
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