Fichas
Exam 2 - Skeletal System and Lymphoid Organs
Fichas del conjunto (125)
- 1What are the primary and secondary functions of bone and cartilage?1': support and locomotion/movement
2': protection, mineral storage, and hemopoiesis - 2What are bone and cartilage derived from? Why are they strong?Primitive mesenchymal cells
Properties of ground substance and extracellular fibers they have - 3Formation of cartilageStellate 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 - 4What is perichondrium?Peripheral zone of dense CT that surrounds cartilage
Contains fibroblasts, collagen, and immature chondroblasts - 5What is interstitial growth?Type of cartilage growth
New cartilage forms within mass and chondrocytes retain the ability to divide - 6What 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 - 7Characteristics of cartilageAvascular 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 - 8What 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 - 9Characteristics of hyaline cartilageHas 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 - 10Characteristics and location of fibrocartilageConsists 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. - 11Characteristics and location of elastic cartilageSimilar 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 - 12Process of cartilage repairLIMITED 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) - 13What is woven bone?Immature form of bone
Characterized by random orientation of collagen fibers - 14What 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) - 15What are trabeculae?AKA spicules
Thin branches of bone surrounded by open spaces (marrow cavity)
Makes up cancellous (spongy) lamellar bone - 16What 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 - 17What is the epiphyses?Ends of long bones
Composed of spongy, cancellous bone covered with hyaline articular artilage - 18What is the metaphysis?Flared region of long bone between the epiphysis and diaphysis
Contains epiphyseal plate ("physis") of long bones - 19What is the periosteum?Layer of fibrous CT that covers the external surface of bone
Contains fibroblasts and osteoprogenitor cells - 20What is endosteum?Lining of internal marrow cavity of bone
- 21What 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 - 22What are osteoprogenitor cells?Resting mesenchymal cells that reside in the periosteum and endosteum
Can differentiate into osteoblasts and osteocytes - 23What 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 - 24What 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) - 25What are osteocytes?Mature "bone cells"
- 26What 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 - 27What 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 - 28What 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 - 29What is calcitonin?Hormone secreted by the thyroid gland
Stimulates osteoblast activity, inhibits osteoclasts => bone deposition
Decreases blood Ca levels - 30What 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 - 31What makes up mature, compact bone?~70% inorganic salts and 30% organic matrix
- 32What 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 - 33What 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 - 34What 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 - 35What 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) - 36What is the cement line?Outer margin of an osteon
- 37What 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 - 38What are Volkmann's canals?Transverse canals that connect the longitudinal Haversian canals in compact bone
- 39How does exchange of waste and nutrients occur in compact bone?Via Haversian vessels that are oriented parallel to the long axis of bone
- 40What are interstitial systems?Inactive Haversian systems in compact bone
- 41What are circumferential lamellae?Organization of the outer periphery of cortical bone
- 42What controls bone growth?Growth hormone, thyroid hormone, and sex hormones
- 43What 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 - 44What 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. - 45Process of endochondral ossification1. 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) - 46Where are the centers of ossification in endochondral oss.?Primary: mid-diaphysis
Secondary (2): epiphyses - 47What 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 - 48What is the last long bone to close in humans?FEMUR
Occurs ~18-20 - 49What 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 - 50Process of intramembranous ossification1. 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 - 51What 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 - 52What 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 - 53When do you need to "set" a fracture?BEFORE provisional callous transforms into bony callous
- 54What 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 - 55Types of synovial cellsType A: resemble macrophages
Type B: resemble fibroblasts - 56What are nonsynovial joints?Joints with limited movement that are joined by dense CT and lack articular surface
Includes syndesmosis, synchondrosis, and symphysis - 57What is a syndesmosis?Dense fibrous tissue between bones
In skull, progressively replaced by bone to become synostosis (aka "sutures") - 58What is a synchondrosis?AKA 1' cartilage joint
Contains single layer of hyaline cartilage
Unites first rib with sternum (only one in human adult) - 59What is a symphysis?AKA 2' cartilage joint
Contains two hyaline cartilage surfaces connected by a fibrocartilage plate - 60What 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) - 61What causes a herniated disc?Damage to annulus fibrosus of intervertebral disc that causes the nucleus pulposus to herniate
Can cause sciatica - 62What is arthritis?Inflammation of joints
- 63What 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 - 64What are osteophytes?AKA bone spurs
Production of irregular new bone at edges of articular surfaces
Limits range of motion - 65What is ankylosis?Bony fusion of joint with loss of mobility
Result of progressive build-up of osteophytes, osteoarthritis, and/or trauma - 66What is rheumatoid arthritis?Local, autoimmune reaction in joints
Causes pain/damage to articular cartilage and thickening/inflammation of synovial membrane - 67What is pannus?Replacement of articular cartilage with fibrovascular tissue
Result of rheumatoid arthritis - 68What 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 - 69What 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 - 70What 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) - 71What 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 - 72What is dense lymphoid tissue?LT organized into discreet structures or organs
E.g. spleen, lymph nodes, thymus, tonsil - 73What is diffuse lymphoid tissue?LT located throughout the body and assoc. with mucous membranes
- 74What is MALT?Lymphoid tissue common in respiratory and digestive tracts
- 75What is 1' lymphoid tissue?Lymphoid tissue where b- and t-cells acquire surface receptors
Bone marrow (b-cells) & thymus (t-cells) - 76What is 2' lymphoid tissue?Where mature b- and t-cells migrate to
- 77Lymphomas vs. leukemiasBoth malignant tumors of immune system
Solid organs: lymphomas
Involve blood: leukemias - 78Characteristics of lymphatic vesselsNetwork 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 - 79What 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 - 80What 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 - 81What is a lymphoid cell?Lymphocytes of all types found in lymph nodes
Derived from bone marrow and enter node via bloodstream - 82What 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 - 83What 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 - 84Morphology of lymph nodesOuter 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 - 85What are medullary sinuses?Broad lymphatic channels in the lymph nodes
Separate the cortex and the medulla - 86What 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 - 87Where do you find high endothelial venules?Deep, inner cortex of lymph node at the corticomedullary junction (AKA paracortical zone)
- 88What 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 - 89What are other names for cortical sinuses?trabecular and peritrabecular
- 90What 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) - 91What 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 - 92What 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) - 93What causes swollen lymph nodes?Proliferation of lymphocytes in lymphoid follicles
- 94What is the mantle zone?Region of antigen presentation in 2' lymphoid follicles
Darker staining rim surrounding germinal center - 95Characteristics of the thymusLobular, 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) - 96From where is the thymus embryologically derived?From epithelial outgrowth of 3rd pharyngeal pouch
Important hematopoietic organ during fetal development!!! - 97Four functions of the thymusProduction 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 - 98As 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 - 99What 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 - 100What 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 - 101What happens to the thymus at puberty?Degenerates (vestigial in adults)
Undergoes fatty infiltration and lymphatic depletion (AKA thymic involution) - 102What 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 - 103What is the largest lymphoid organ in the body?Spleen
- 104What 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 - 105What happens if the spleen is removed?Function taken over by liver and bone marrow
- 106Histology of spleenDense, 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 - 107What 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 - 108What supports pulp cords in red pulp in spleen?CT skeleton of reticular cells and reticular fibers
- 109What 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 - 110What 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 - 111What are splenic nodules?Enlarged germinal centers visible to the naked eye
AKA area of white pulp that has a germinal center - 112What 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) - 113Open circulation model of spleenBranches 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 - 114How 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 - 115What are stave cells?Endothelial cells that line the sinusoids in the spleen
Slits between these cells allow free passage of blood cells - 116What is Waldeyer's ring?Collective term for palatal, lingual, and pharyngeal tonsils
Forms ring of immunologic protection of GI and respiratory tracts - 117What 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) - 118What are lingual tonsils?Tonsils present at base of tongue and pharyngeal tonsils (AKA adenoids) in nasopharynx
Associated with Eustacian tubes - 119What is NALT?Nasal-associated lymphoid tissue
Collective term for the palatal and pharyngeal tonsils - 120What covers the luminal surface of palatine and lingual tonsils?Stratified squamous non-keratinized epithelium
Invades the tonsil, forming blind-ended TONSILAR CRYPTS - 121What 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 - 122What 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 - 123What 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 - 124When is MALT formed? When is it at max distribution?Formed during fetal development
Distribution max in childhood and progressively atrophies with age - 125What 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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- DDS (Exam 2) Histology - DDS Fichas sobre Exam 2 - Skeletal System and Lymphoid Organs, creado por Brianne Schmiegelow el 12/10/2017.
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