Exam II Flashcards
(248 cards)
1
Q
What are the three major classes of cartilage?
A
- hyaline
- elastic
- fibrocartilage
2
Q
What are the basic components of cartilage?
A
cells
- chondroblasts (cartilage forming)
- chondrocytes (cartilage maintenance)
extracellular matrix
- collagen fibers (mostly type II, fibro -> I)
- amorphous ground substance
3
Q
What are the functions of cartilage?
A
- compressible
- resists distortion
- absorbs shock in joints
- reduces friction in movable joints
- necessary for endochondral bone growth
- involved in bone fracture repair
4
Q
What are the characteristics of cartilage?
A
- avascular
- formation
- perichondrium
- isogenous groups
- unique matrix
5
Q
What three components are needed for cartilage formation?
A
- chondroblasts (lay down cartilage matrix and become chondrocytes)
- chondrocytes (maintain cartilage matrix)
- lacunae (pockets within the matrix where the chondroblasts and chondrocytes are found)
6
Q
How does cartilage receive the proper nutrition?
A
nutrients and O2 are derived from blood vessels that surround the cartilage and must diffuse through the matrix to the cells
7
Q
What are the layers of the perichondrium?
A
-outer fibrous layer
+contains fibroblasts
-inner fibrous layer
+gives rise to chondroblasts -> chondrocytes
+chondrocyte involved in production of collagen and proteoglycans in matrix. Also makes chondronectin
8
Q
What are isogenous groups?
A
- groups of 2-8 chondrocytes that occupy the same lacunae, results from mitotic division
- cells separate as they begin to lay down the matrix
9
Q
What are the different matrices of cartilage? What are the components?
A
Components:
- collagen type II (type I in fibrocartilage)
- hyaluronan (hyaluronic acid)
- chondroitin sulfate, keratin sulfate, heparin sulfate
- glycosaminoglycans
Types:
- territorial matrix (surrounds each chondrocyte, high GAG content, low collagen content)
- inter-territorial matrix (surrounds territorial matrix, low GAG content and high collagen content)
10
Q
What are the characteristics of hyaline cartilage?
A
-most common type
-avascular
-type II collagen
-surrounded by perichondrium
-translucent, bluish gray to white
-solid but flexible
-chondrocytes are often found in cell groups
appositional and interstitial growth patterns
11
Q
Where is hyaline cartilage located?
A
- external auditory meatus
- larynx
- tracheal cartilages
- bronchial cartilages
- fetal long bones
- articular ends of bones
12
Q
What are the characteristics of elastic cartilage?
A
- specialized by the addition of elastic fibers to the matrix
- surrounded by perichondrium
- yellow color -> elastic fibers
- more opaque, flexible, and elastic than hyaline
- chondrocytes located singly
- type II + elastic
13
Q
Where is elastic cartilage found?
A
- auricle
- epiglottis
14
Q
What are the characteristics of fibrocartilage?
A
-increased collagen in matrix
-reduced cellularity compared to hyaline
not surrounded by perichondrium
-opaque due to fibrous texture
-type I collagen
-single sparse chondrocytes
15
Q
Where is fibrocartilage located?
A
- intervertebral discs
- pubic symphysis
- insertion of some tendons and ligaments
- closely associated with dense connective tissue or hyaline cartilage
16
Q
What are the characteristics of bone tissue?
A
-based on canalicular system
-highly vascular and found close to capillaries
-increase in bone length occurs though appositional growth of hyaline cartilage model
bone tissue is contrinually resorbed, reconstructed, and remodeled
-formed by osteoblasts -> osteocytes
-two major components (organic -> osteoid, inorganic -> hydroxyapatite, 35-65% of bone)
17
Q
Appositional vs interstitial growth
A
Appositional:
-growth in thickness due to addition of more extracellular matrix
Interstitial:
-growth from a number of different areas within a structure, typically grows lengthwise
18
Q
What are the three different types of bone?
A
- woven bone (occurs during bone development and repair)
- compact bone (lamellar bone)
- spongy bone (trabecular or cancellous bone)
19
Q
What is the structure of compact bone?
A
- lacks cavities and forms dense plates on outside of long bone or flat bones
- consists of concentric (Haversian) lamellae which encircle a blood vessel and nerves forming an osteon, Haversian system
- osteocytes are found between the lamellae in lacunae and are connected to each other and Haversian canal via canaliculi
- Volkmann’s canals run perpendicular to Haversiann canals and connect the Haversian canals to each other and the surface
20
Q
What is the structure of trabecular/spongy bone?
A
-3D lattice of branching, bony spicules intertwined to form trabeculae surrounding the bone marrow spaces and in the long and flat bones
21
Q
What are the macroscopic bone structures?
A
- periosteum
- marrow (medullary) cavity
- endosteum
- Sharpey’s fibers (bundles of collagen fibers that nail the tendons and ligaments to the bone)
22
Q
What are osteoprogenitor cells?
A
- stem cells that in the adult are described as bone lining cells
- adult, found in the inner portion of the periosteum, endosteum, and lining vascular canals of compact bone
- derived from mesenchyme of the embryonic somite (sclerotome) and possess mitotic potential
- give rise to osteoblasts and bone lining cells
23
Q
What are osteoblasts and what do they secrete?
A
- derived from osteoprogenitor cells and give rise to osteocytes
- characterized by alkaline phophatase, vitamin D3
Major protein products: -type I collagen -osteocalcin -osteonectin -osteopontin -osteoprotegerin RANKL
24
Q
What are osteoclasts?
A
-derived from monocytes and “eats” bone
25
How are osteoblasts regulated to control the osteoclasts?
- Parathyroid hormone (PTH) is the primary regulator
- at low PTH levels, bone formation by osteoblasts is stimulated
- at high PTH levels, osteoblasts are stimulated to release osteoclast-differentiation factors
- PTH stimulates the differencetion of monocyte precursors to form osteoclasts. Also stimulates the formation of ruffled borders on osteoclasts
- elevated PTH leveles result in eroded bone and fibrosis of the resulting spaces -> OSTEITIS FIBROSA
26
How do the osteoblasts regulate the osteoclasts?
- PTH binds to osteoblast
- osteoblast stimulated to synthesize M-CSF and RANKL
- osteoblast release M-CSF
- M-CSF binds to the M-CSF receptor on the monocyte
- monocyte is a macrophage and expresses RANK
- RANK binds to RANKL (couples osteoblast and macrophage)
- macrophage becomes multinucleated immature osteoclast
- osteoblast secretes osteoprotegerin ( osteoprotegerin binds to RANKL with greater affinity than RANK, inhibits osteoclast maturation, PTH blocks the synthesis of osteoprotegerin)
- a non-functional osteoclast uncouples from the osteoblast and becomes a functional osteoclast
- calctonin acts to reduce bone resorption
27
What does the skeletal system of vertebrates begin as?
cartilage
28
Which of the following is not a characteristics of fibrocartilage?
a) type II collagen
b) not surrounded by perichondrium
c) found in intervertebral discs
d) increased collagen in the matrix
e) neither A nor B are characteristics
a
29
Which of the following is not part of a Haversian system?
a) periosteum
b) lacunae
c) lamellae
d) Volkmann canal
e) canaliculi
a
30
Parathyroid hormone stimulates osteoblasts to secrete/express which of the following?
a) osteoprotegrin
b) M-CSF
c) RANKL
d) all of the above
e) only B and C
e
31
How do osteoclasts function to break down bone?
1. Around ruffled border actin filaments create a sealing zone with integrin and osteopontin.
2. A chloride channel prevents an excessive rise in intracellular pH.
3. Bicarbonate is exchanged for chloride, which is transported to the chloride channel (on ruffled border) to Howship's lacuna. This channel allows for electroneutrality.
4. Carbonic anhydrase II generates H+ via H2O and CO2. H+ is released into Howship's lacuna via H+ ATPase pump to maintain an acidic environment, stabilizing mineralized bone.
5. Cathepsin K is released into Howship's lacuna is break down the organic material, followed by acidification of inorganic materials.
32
How is intramembranous bone formed?
-aggregation of mesenchymal cells controlled by signals (Wnt, Hedgehog, FGF, TGF-beta)
-mesenchymal cells differentiate into osteoblasts
-osteoblasts secrete osteoid, trapping some of the osteoblasts -> blastema
-trapped osteoblasts turn into osteocytes (form a functional syncytium)
-mineralization occurs via Ca+2
-osteoblasts form an epithelial-liek covering over the surface of primary bone tissue and can secrete more osteoid on the surface (collagen and non-collagen proteins)
-primary ossification center becomes trabecula
-trabecula fuse together to form spongy bone
-initial bone is woven bone (collagen arranged randomly)
-collagen fibers a aligned creating a lamellar
-lamellae become symmetrically arranged around a blood vessel forming an osteon/Haversian system
-membrane bone usually consists of two layers of compact bone enclosing spongy bone (diploe)
-
33
How is endochondral bone formed?
Cartilage is REPLACED by bone!
- primary ossification center occurs in diaphysis of cartilage
- chondrocytes become hypertrophic
- chondrocytes secrete vascular endothelial growth factor
- blood vessels break through perichondrium, brining osteoprogenitor cells
- hypertrophic chondrocytes undergo apoptosis, leaving behind strands of calcified matrix
- osteoblasts use calcified strands as substrates for deposition of osteoid
- osteoid is calcified
- cells derived from initial perichondrium begin to secrete osteoid appositionally (perichondrium -> periosteum)
- secondary ossification centers occur in epiphyses
- epiphyses and diaphyses are separated initially by epiphyseal plate (growth plate)
34
Describe how endochondral bone is formed in a macro sense.
occurs within a hyaline cartilage model, REPLACES cartilage
1. avascular cartilage becomes vascularized, resulting in breakdown and rearrangement of cartilage matrix
2. diaphysis is reduced to a honeycomb network
3. The network of cartilage is calcified by the deposition of calcium salts
4. Osteoblasts use the calcified cartilage matrix as a framework for bone deposition
5. Periosteum lays down periosteal bone on top of endochondral bone (diameter increases)
6. Additional ossification centers occur in the epiphysis, epiphysis is separated from the diaphysis by a plate of hyaline cartilage (epiphyseal plate)
7. Osteoclasts break down bone in the middle forming the medullary cavity, more cartilage is added to the distal end of the epiphyseal plate
8. Cartilage at proximal end of epiphyseal plate is replaced by bone, bone increases in length
9. When cartilage formation in the plate is overtaken by bone replacement , growth stops and the plate fuses to the shaft.
10. Cartilage at either end of the bone remains as articular cartilage
35
What are the 4 zones found in endochondral bone formation and what are their purposes?
distal to proximal of bone growth:
reserve zone: contains the chondrocytes
zone of proliferation: where the chondrocytes proliferate
zone of hypertrophy and calcification: where the chondrocytes grow and die, leaving calcium deposits
zone of ossification
36
What do the hypertrophic chondrocytes do?
- form calcified matrix
- synthesize type X collagen
- secrete vascular endothelial GF
- signal perichondrial cells to become osteoblasts
37
What is a joint?
where two bones come together
38
What are the three classifications of joints and their subclasses?
- cartilaginous joints (amphiarthroses) -> symphysis and synchondrosis
- fibrous joints (synarthroses) -> suture, gomphosis, syndesmosis
- synovial joints (diarthroses)
39
Describe cartilaginous joints and the subclasses.
bones joined by hyaline or fibrocartilage
symphysis: joined by fibrocartilage
ex. intervertebral discs and pubic symphysis
synchondrosis: joined by hyaline cartilage
ex. epiphyseal plates and first sternocostal joint
40
What are the characteristics of fibrous joints and their subclasses?
- bones joined by collagenous and/or elastic fibrous CT
suture: joints between bones of calvaria
gomphosis: "peg in socket" joint such as teeth in the alveoli
syndesmosis: bones are joined by an interosseous fibrous membrane such as the fibrous membrane between the tibia and fibula
41
What are the characteristics of synovial joints?
- moveable joints exemplified by a connective capsule surrounding a fluid filled joint space
- often reinforced by thickenings of the outer part of the capsule referred to as the ligaments
- ligaments stabilize the capsule and the joint
- ligaments control and restrict direction and range of motion
42
What are the types of synovial joints and how are they classified?
-classified by degree of movement
movement in one plane (monoaxial):
- hinge joints include humeroulnar and knee
- pivot joints include atlantoaxial and radioulnar
- movement in two planes (biaxial)
- condyloid joints include metacarpophalangeal and atlantooccipital
- a saddle sellaris) joint is exemplified by the first carpometacarpal
- movement in three planes (triaxial):
- include ball and socket joints such as glenohumeral and femoroacebular joints
43
What are the parts of the synovial joint and be able to identify on an image.
-cavity
-capsule
+outer fibrous (innervated)
+inner synovial (vascularized)
-ligaments (thickenings in the fibrous capsule attached by Sharpey's fibers)
-synovial fluid (dialysate located in the synovial cavity)
-articular cartilage
44
What is the histology of the synovial joint?
articular cartilage:
- hyaline cartilage
- lacks perichondrium
- not lined by synovial membrane
joint capsule:
- vascularized dense CT
- lined by synovial membrane
- attached to edges of articular cartilage
synovial membrane:
- highly vascularized (fenestrated capillaries)
- 1-3 layers of synovial cells
- no basal lamina
synovial fluid
- contains mucin (hyaluronic acid protein complex)
- produced by synovial cells
- almost friction free surface
synovial cells:
- type A (macrophage like)
- type B (fibroblast like)
45
What percentage of weight does blood have in the body? What is the pH of blood?
- 8%
| - 7.35-7.45
46
What is plasma and serum?
plasma: blood minus the formed elements
serum: plasma without the blood clotting proteins, lacks fibrinogen
47
What are the three layers in heparinized, centrifuged blood?
- supernatant (plasma)
- buffy coat (leukocytes)
- precipitate/hematocrit (RBC)
48
What are the blood proteins and their characteristics discussed in class?
- fibrinogens: made in liver, function in blood clotting, target for thrombin
- albumins: made in liver, exert major osmotic pressure on blood vessel walls
- globulins: immunoglobins
49
What are the characteristics of erythrocytes?
- more in males than females
- numbers increase under the influence of erythropoietin (produced by the kidney)
- devoid of granules and organelles
- content: lipids, ATP, carbonic anhydrase, hemoglobin
- proteins: 50% integral membrane proteins, peripheral proteins (spectrin and actin bound to ankyrin)
50
What is hereditary spherocytosis?
RBCs are spherical, rigid, and more likely to be destroyed in the spleen. Caused by cytoskeletal abnormalities involving sites of interaction between spectrin and protein 4.1
51
Describe the structure and organization of actin filaments in the erythrocyte.
- have no nucleus or organelles, so plasma membrane and proteins are easily isolated
- cortical cytoskeleton is the primary cell shape determinant
- major structural protein is spectrin (calponin actin binding family)
- tetramer of alpha and beta chains. Spectrin tetramers associate with short actin filaments resulting in spectrin-actin network
- ankyrin links the spectrin-actin network and the plasma membrane by binding to spectrin and a transmembrane protein (band 3)
- protein 4.1 is another link that binds spectrin-actin junctions and the transmembrane protein glycophorin
52
What are the characteristics of neutrophils?
polymorphonuclear leaukocytes
-7-9 micro
-3-5 nuclear lobes with connecting strands
-active ameboid phagocytes
-small, numerous specific granules
+larger, less numerous azurophilic granules
-remain in circulation for 10-12 hours
-live for 1-2 days after leaving circulation
-secrete enzymes capable of destroying certain bacteria by formation of free radicals (superoxide) as well as release of lysozyme and lactoferrin -> destroy bacterial walls
53
What is found in the granules of a neutrophil?
primary/azurophilic: elastase and myeloperoxidase
secondary: lysozyme and proteases
54
What are the characteristics of basophils?
-7-9micro
-lobulated nucleus (bilobed)
-large, membrane bound basophilic granules:
+contain vasoactive substances (serotonin, heparin, and kallikrein) and can produce leukotrienes (increase vascular permeability and slow contraction of smooth muscles)
55
What are the characteristics of an eosinophil?
-9-10micro
-bilobed nucleus
-specific granules
+major basic protein (disrupts parasite membranes and causes basophils to release histamine)
+peroxidases
+cationic protein (neutralizes heparin and is anti-parasitic)
-repsond in allergic diseases and parasitic infections
-phagocytize antibody-antigen complexes and parasites
56
What are the characteristics of lymphocytes?
- large round, sometimes slightly indented nucleus, fills most of the cell
- variation in cell size (6-18micro)
- B lymphocytes (precursor of plasma cell)
- T lymphocytes (precursor of T lymphocytes)
57
What are the characteristics of monocytes?
-9-12micro
largest leukocytes
-eccentrically located nucleus
-granular cytoplasm due to small lysosomes
-precursor of macrophages and osteoclasts
58
What are the characteristics of platelets?
- derived from megakaryocytes (bone marrow)
- 2micro
- 200,000-4000,000 per microliter of blood
- enhance aggregation by release factors and they promote clot formation, retraction, and dissolution
- repair damage to endothelium by forming platelet plug
- adhesion of platelets involves integrins
- endothelial cells release prostacyclin which decrease platelet aggregation
59
What is the site of synthesis of most of the proteins of the clotting cascade?
LIVER
-vitamin K is essential in the synthesis of factors VII, IX, and X
60
What is hemostasis?
- the elimination of bleeding
- most effective in small vessels
- -accumulation of blood in tissues is a hematoma(bruise)
61
What is the sequence of events of hemostasis in small vessels?
- constriction of smooth muscle around vessels
- constriction of vessels
- slowing of blood
- formation of platelet plug
- blood clotting
62
Why is a platelet plug not formed all the time?
- platelets do not normally adhere to the endothelial cells that line the blood vessel walls
- due to the fact that untraumatized platelets produce prostacyclin from arachidonic acid
- in an injury, the endothelial lining is disrupted, exposing the underlying collagen fibers
63
How is a platelet plug formed?
- platelets adhere to the collagen and release the contents of their secretory vesicles, including ADP, and also cause the conversion of arachidonic acid in the platelet plasma membrane to thromboxane A2, which further stimulates platelet aggregation
- ASDP and other factors cause the platelets to aggregate, forming a plug
- Von Willebrand factor is a plasma protein, released from Weibel-Palade bodies in endothelial cells that facilitates the adherence of platelets to the walls of the damaged blood vessel
64
What are the steps in blood clotting?
1. Activation of prothrombin (activated by factor XII, factor XII is activated by the collagen of damaged walls)
2. prothrombin to thrombin -> thrombin catalyzes the conversion of fibrinogen to fibrin
3. converts fibrinogen to fibrin (formed by factor XIII). Fibrin creates a meshwork that traps platelets, blood cells and plasma to form clot.
4. Reshaping of the clot by polymerization of fibrin (fibrinogen polypeptides chemically linked by factor XIII)
5. Fibrinolysis: dissolution of fibrin clots through activation of the plasminogen activator system and the action of plasmin.
+cascade of protein plasminogen activators convert inactive plasminogen to plasmin. t-PA is one of the activators secreted by the endothelial cells. Fibrin initiates it's own destruction. Plasmin and t-PA dissolve the clot
65
What are the two cascade sequences?
intrinsic and extrinsic pathways, artificial separation -> actually interconnect
66
What is the intrinsic pathway?
typically initiated by injury to the endothelium of the blood vessel exposing collagen fibers. Everything necessary for it to occur is already within the blood. including calcium, required as a cofactor for many of the sequential steps in the clotting cascade.
67
What is the extrinsic pathway?
involves the formation of tissue factor (thromboplastin or Factor III)
68
What is thromboplastin?
a membrane bound lipoprotein expressed at sites of cell injury. It is derived from the plasma or organelle membranes of damaged cells in the disrupted tissue and enters into the circulating blood.
69
What is the pathway of the intrinsic pathway?
1. injury to the endothelium of blood vessel exposing collagen fibers leads to the activation of factor XII (Hageman factor)
2. factor XII activates factor XI and converts prekallikrein to kallikrein
3. Activated XI activates factor IX
4. activated factor IX combines with activated factor VIII and calcium to activate factor X
* **thrombin is involved in the activation of factor XI and VIII
70
What is kallikrein used for the in the intrinsic pathway?
- involved in the formation of bradykinin (increase vascular permeability) and in the kinin cascade and the in the conversion of plasminogen to fibrin
- can also feedback and activate more Hageman factor
71
What are the steps in the extrinsic pathway?
- damaged cells from injured tissue release thromboplastin into the blood
- thromboplastin activates factor VII
- Factor VII and calcium activate factor X
72
What are the steps in the common pathway?
-intrinsic and extrinsic pathways lead to the common pathway
1. Factor X combines with factor V and calcium to activate prothrombin
+thrombin activates inactive factor V
2. prothrombin(inactive factor II) -> thrombin
3. thrombin with calcium converts fibrinogen to fibrin
4. thrombin with calcium activates factor XIII
5. activated factor XIII is necessary in the cross linking of fibrin polymers to stabilize fibrin gel
73
What leukocyte extravasation?
- a homing mechanism that is activated by various cytokines released by mast cells, platelets, and damaged tissue cells
- NO is released by endothelial cells and increase vascular permeability
- leukocytes neutrophils) leave the laminar flow and move toward the endothelium of the vessel wall
74
What are the two phases of leukocyte extravasion?
- selectin phase
| - integrin phase
75
What occurs during the selectin phase of leukocyte extravasion?
- sialyl Lewis-x antigens are oligosaccharide ligands for P-selectin binding found on leukocyte membranes
- P-selectin appears on the cell surface when endothelial cells are activated by inflammatory signaling
- oligosaccharide ligands on leukocytes bind to carb recognition domains (CRDs) on the P-selectins (from Weibel-Palade bodies)
- binding of ligands to the P-selectins causes leukocytes to roll along the endothelium
76
What occurs during the integrin phase of leukocyte extravasion?
- integrin receptors are activated on leukocyte membrane ICAM-1 and ICAM-2 [Ig superfamily])
- integrins beta1 and beta2 are activated on leukocyte membrane and bind to VCAM and ICAM on endothelial cell membranes
- integrins interacting with endothelial ligands promote the transendothelial migration leukocytes
77
What is erythroblastosis fetalis? What are the causes and treatments?
-antibody induced hemolytic disease in the newborn that is caused by blood group incompatibility between mother and fetus
Cause:
-fetus inherits RBC antigenic determinants that are foreign to mother (Rh+ fetus, Rh- mother) -> caused by D antigen
-first pregnancy ok until blood is mixed and mother creates the antibodies to the Rh factor
Treatment:
-mother is given anti-D globulin after birth of Rh+ baby. Anti-D antibodies mask the antigenic sites on the fetal RBCs that may have leaked into the maternal circulation during childbirth
-hemolysis results in:
+hemolytic anemia which causes hypoxic injury to the heart and liver leading to generalized anemia (hydrops fetalis)
+jaundice -> damage to CNS
+hyperbilirubinemia
78
What are some characteristics of stem cells?
- proliferate extremely well
- self-renewing
- differentiate into several different cell types (at least 2)
- reconstitute tissues after injury
79
What is the difference between totipotent vs pluripotent vs multipotent?
totipotent: give rise to all cells of an organism, including embryonic and extraembryonic (supports embryonic development). Zygote is totipotent.
pluripotent: give rise all cells of the embryo and subsequently adult tissues (embryonic stem cells)
multipotent: give rise to different cell types of a given lineage (adult stem cells)
80
What are the two different types of stem cells?
embryonic stem cells:
- derived from ICM of blastocyst
- pluripotent, differentiate to all cell lineages
- technical and ethical limitations
- may be induced from adult tissues
Adult:
- harvested from mature organs/tissues (bone marrow)
- multipotent-more restricted ability to produce different cell types and to self-renew
81
Where are the hematopoietic sites during development?
2-8 weeks:
- islands of hematopoiesis (blood islands) -> nucleated erythrocytes
- no leukocytes during this phase
8-28 weeks:
- liver and spleen
- ceases around birth
6 months and beyond:
-bone marrow
82
Where are blood cells synthesized before and after puberty? Are blood cells synthesized anywhere else in the body?
prior puberty:
-skull, ribs, sternum, vertebrae, clavicles, pelvis, long bones
after puberty:
-same as above minus long bones, eventually marrow turns to yellow marrow and blood cell production is limited to sternum and iliac crest
- extramedullary hemapoiesis:
- in certain disease states, blood cell formation may occur in liver and spleen
83
What are the structures discussed during bone marrow histology? Characteristics?
stroma:
-contains fibroblasts, reticular cells, adipose cells, and endothelial cells
-synthesizes and secretes hematopoietic growth factors
parenchyma:
-consists of various lineages of hematopoeitic cells in different stages of differentiation
sinusoids:
-endothelial-lined spaces that connect arterial and venous vessels
-provides access for mature blood cells to move into circulation
hematopoietic cords:
-bands of parenchyma and stroma lying between the sinusoids
84
What is the distribution of hematopoietic cells produced?
-60% granulocytopoeisis
-30% erythrocytopoiesis
10% thrombocytopoiesis, monocytopoiesis, cytopoiesis
85
myeloid/erythroid ratio?
total volume of cells in granulocytopoiesis/ total volume of cells in erythrocytopoiessi
3: 1 normal
8: 1 chronic myelogenous leukemia
1: 5 polycythemia
86
How to mature blood cells migrate out of the bone marrow?
hematopoietic cords -> sinusoidal endothelial walls -> sinusoids
87
What is a niche and how does it affect stem cell differentiate?
- niche= microenvironment
| - factors and environmental thingies influence how stem cells differentiate
88
What are characteristics of hemopoietic stem cells?
-are pluripotential (committed to either myeloid or lymphoid stem cell lines)
-can self-renew
-produce two kinds of multipotential precursor cells:
+myeloid stem cells- give rise to all blood cell lines except lymphocytes
+lymphoid stem cell- give rise to lymphocytes
-cannot be identified by morphology but can be recognized by cell surface markers
89
How can leukocytes be classified?
granulocytes
- neutrophils
- basophils
- eosinophils
agranulocytes
- monocytes
- lymphocytes
90
What are the 5 kinds of CFU that myeloid stem cells give rise to?
- erythroid
- megakaryocyte
- basophil
- eosinophil
- granulocyte-macrophage
91
What are the myeloid stem cell derivatives and what factors affect them?
erythroid (erythropoietin) -> proerythroblast
megakaryocyte (thrombopoietin) -> megakaryocytoblast
GM-CSF -> basophil (SFC) -> myeloblast
GM-CSF -> eosinophil -> myeloblast
GM-CSF -> granulocyte-macrophage (G-CSF) -> neutrophil
(M-CSF) -> monoblast
92
What are the two kinds of lymphoid stem cells adn where do they mature?
- T cell progenitor (thymus)
| - B cell progenitor (bone marrow)
93
How is a granulocyte-macrophage formed (stages)? macrophage
monoblast -> promonocyte -> monocyte -> macrophage
- monoblast- can divide
- monocytes are found in circulation
94
How is a granulocyte-macrophage formed (stages)? neutrophil
myeloblast (d) -> proyelocyte (d) -> myelocyte (d) -> metamyelocyte -> band cell (c) -> neutrophil (c)
d: divide
c: circulation
95
How is a basophil and eosinophil formed (stages)?
myeloblast (d) -> promyelocyte (d) -> myelocyte (d) -> metamyelocyte -> band cell (c) -> eosinophil or basophil (becomes mast cell) (c)
96
How are platelets formed (stages)?
megakaryoblast -> megakaryocyte -> platelets (c)
97
How are erythrocytes formed (stages)?
proerythroblast (d) -> basophilic erythroblast (d) -> polychromatophilic erythroblast (d) -> orthochromatic erythroblast -> reticulocyte (c) -> erythrocyte (c)
98
Where are hemopoietic growth factors produced?
- endothelial cells in marrow
- fibroblasts
- stromal cells
99
What are the three major groups of hematopoietic growth factors?
- colony-stimulating factors
- erythropoietin and thrombopoietin
- cytokines (primarily interleukins)
100
What are the characteristics of colony stimulating factors?
- produced by endothelial cells, T cells, fibroblasts, and monocytes
- stimulates granulocytopoiesis and monocytopoiesis
- ameliorates neutropenia associated with chemotherapty or radiation -therapy synthetic form: sargramostim or melgramostim
101
Differentiate between G-CSF and M-CSF.
G-CSF:
- produced by endothelial cells, fibroblasts, and macrophages
- directs CFU-G to proliferate and differentiate into myeloblasts
- may be used following chemotherapy or radiation to treat neutropenia
M-CSF:
-commits CFU-GM to monocyte pathway
102
Characteristics of erythropoietin.
-directs CFU-E to proliferate and differentiate into proertyhroblasts
-produced in kidney in response to decrease in oxygen saturation
-secondary polycythemia is any abnormal increase in total RBC mass resulting from hypoxia and stimulating release of erythropoietin
+causes include smoking and Teralogy of Fallot
103
Characteristics of thrombopoietin.
- directs formation of megakaryoblasts
- produced in proximal convoluted tubule
- produced in parenchymal cells and sinusoidal endothelial cells of liver
- no therapeutic use
104
Characteristics of cytokines.
-mediate positive and negative effects on cellular quiescence, apoptosis, proliferation, and differentiation
-engage specific receptors and activate a variety of signaling pathways
ex
-interleukin-3
-GM-CSF
-Fit-3 ligand
-Kit ligand
105
What are components of the ECM?
- heparin sulfate
- collagen
- laminin
- fibronectin
106
Chemokines
- regulate blood cells trafficking and homing to sites of need
- may serve as positive and negative growth regulators
- bind to guanine protein-coupled transmembrane receptors
107
What are the three muscle types?
- skeletal
- smooth
- cardiac
108
What are some characteristics of skeletal muscle?
-multinucelated
-peripheral nuclei
-sarcomeric arrangement
-single motor axon innervates one fiber
-all or none contraction
contains troponin C
-formed during embryonic development when myoblasts join end to end to form a myotube
-myotube matures into myocyte with hundreds of nuclei
-each myocyte is 50-60micro in diameter
109
What are the different types of muscle fibers? What are their characteristics?
Type I (slow twitch):
-intense staining for oxidative enzymes
-rich in NADH transferase, myoglobin, ATPase
-possess many mitochondria
-primarily utilize oxidative phosphorylation-produce slow and continuous contractions
Type IIA:
-intermediate staining for oxidative enzymes
-utilize both aerobic and anaerobic respiration for ATP production
-contract more rapidly than type I fibers
-resistance to fatigue
Type IIB (fast twitch):
-light staining for oxidative enzymes
utilize primarily anaerobic respiration for ATP production
-contact more rapidly than type I or Type IIA fibers
-fatigue quickly
110
What are some characteristics of smooth muscle?
- single mononucleated cells
- no sarcomeric arrangement
- cells innervated via ANS
- do not respond to all or none
- cells connected via gap junctions
111
What are the characteristics of cardiac muscle?
- mononucleated cells
- centrally positioned nuclei
- cells branched
- sarcomeric arrangement
- cells communicate via gap junctions intercalated discs)
- cells not directly innervated
112
What are the connective covering of the muscle composed of?
epimysium: type I collagen that blends into tendon
perimysium: fibroblasts and type I collagen
endomysium: consists of basal lamina and reticular collagen fibers
- basal lamina is secreted by muscle cells
- basal lamina anchors muscle fiber to each other
- basal lamina helps distribute the force of contraction
113
Describe the different parts of a myosin.
-myosin is a dimeric protein with long tails and two heads at one end
-each head has:
+actin binding region
+ATP binding region
+light chain binding region
-two pairs if light chains:
+similar to calmodulin but have lost the ability to bind calcium
+essential light chains
+regulatory light chains (required to maintain stability of myosin II, sites for P binding)
114
Describe the elements of an actin molecule.
F actin
-polymer of G actin
-filament consists of two polymers wound in an alpha-helix configuration
-plus end inserts on Z disc
Actin associated molecules
-troponin
-tropomyosin
+each sits in the groove between two actin strands of an actin filament
+each tropomyosin spans 7 actin monomers
115
What are the three types of troponin and what is it's function?
- troponin I: inhibits binding between actin and myosin
- troponin C: binds calcium ions
- troponin T: binds to tropomyosin
116
What are the components of the cytoskeleton?
- a(beta)-crystallin
- dystophin
- dystroglycan complex
- alpha-actinin
- titin
- nebulin
- desmin intermediate filaments
- plectin
117
Function of A(beta)-crystallin?
-heat shock protein that protects desmin from mechanical stress
118
Function of dystrophin?
- one of the proteins that links the alpha-actinin/desmin complex to cytoplasmic side of sarcolemma
- anchors actin to sarcolemma
- reinforces sarcolemma during muscle contraction
119
Function of dystroglycan complex?
-links dystrophin (intracellular) to laminin-2 (extracellular)
120
Function of alpha-actinin?
-attaches thin filaments to the Z line
121
Function of titin?
- large fibrous protein
- extends from Z-disk to middle of H-band and connects ends of thick filaments to Z-line
- provides myosin with elasticity
- centers thick filaments in the sarcomere
122
Function of desmin intermediate filaments?
- framework of desmin filaments which surrounds the Z line and extends into each sarcomere
- links myofibrils laterally and to the sarcolemma
123
Function of plectin?
-binds desmin filaments
124
Function of nebulin?
- extends from Z disc to end of actin filament
| - serves as template to regulate length of actin ffilament
125
What is dystrophin and how does this contribute to muscular dystrophy?
- links actin filaments to transmembrane proteins of muscle cell plasma membranes
- the transmembrane proteins link to the extracellular matrix, which helps maintain cell stability during muscle contraction
- muscular dystrophy, X-linked inherited disease, results in progressive degeneration of skeletal muscle
- dystophin is either absent or abnormal in patients with Duchenne's or Becker's muscular dystrophy
126
What are satellite cells? What are their function?
-attach to myotubes before basal lamina is laid down
-generally quiescent
-function as stem cells
-can become mitotic in times of stress
+C-Met receptor (binding site for hepatic growth factor)
+HGF
-give rise to myogenic precursor cells
+replace damaged muscle of proliferating, fusing, and differentiating into skeletal muscle
127
What are the components of a neuromuscular spindle?
```
>extrafusal fibers
>intrafusal fibers
-nuclear bag region is the sensory region
-nuclear bag fibers
-nuclear chain fibers
>alpha motor neurons
-to extrafusal fibers
>gamma motor fibers
-to intrafusal fibers
>primary and secondary afferent fibers (sensory)
```
128
What is the composition of the intercalated discs in the cardiac muscle?
```
-macula adherens (desmosomes)
+link intermediate filaments (desmin) of adjoining cardiac muscle cells
+part of transverse component
-fascia adherentes
+anchor actin filaments of sarcomeres
+part of transverse component
-gap junctions
+longitudinal component
```
129
What do atrial natriuretic peptides do?
- secreted by cardiac muscle cells in atria
- regulate fluid electrolyte balance
- relax vascular smooth muscle (reduce blood vol and pressure)
- stored as prohormone in secretory vesicles
- release is stimulated by atrial stretch (cleavage of prohormone)
130
How are the components of smooth muscle arranged?
- actin and myosin bundles are incorporated into a meshwork -> found throughout cytoplasm except in nuclear area
- dense bodies:
- anchor actin filaments to each other and cell membrane
- contain alpha-actinin
- interconnected by a specific type of desmin
- communicate force of contraction to cytoskeleton and cell membrane
- found in cytoplasm and in the cell membrane
131
How does smooth muscle get the Ca+2 needed for contraction?
- no T tubule system or extensive SR
| - pinocytotic vesicles -> transport Ca+2 from extracellular fluids to SR
132
What is the role of the lipd rafts and caveolae in smooth muscle cells?
- permanent depressions of the cell membrane that are involved in fluid and electrolyte transport
- preceded by membrane lipid rafts composed of cholesterol and sphingolipids
- caveolae binds to the cholesterol in the lipid rafts and initiates the formation of caveolae
- vesicles that are formed detach and participate in vesicular trafficking
133
What are the different types of signals smooth muscle can receive?
- adrenergic and muscarinic: linked to G proteins
- nicotinic cholinergic: cation channel
-excitation is spread through numerous gap junctions
134
What are the different structures found in neural development? What is their histology?
-neural plate
+composed of simple columnar epithelium
+cell shape is maintained by microtubules
neural folds
+columnar to wedge cell shape
+shape change due to actin filaments
+wedge shape of cells caused flattened neural plate to bend
+bends can be up or down depending on whether apex of wedge-shaped cells are pointed up or down
135
What are the stages of development?
- neuroepithelial cells from embryonic neuroectoderm give rise to neuroblasts
- neuroblasts give rise to neurons of the central nervous system (brain and spinal cord)
- neural crest cells are derived from the neuroectoderm and give rise to neurons and neuroglial cells of peripheral nervous system
136
What is the difference between anterograde and retrograde transport?
Anterograde:
-cell body toward distal end of axon
-utilizes kinesin
1) slow rate at 1-6mm per day
-two systems
+SCa (slow component a) - preassembled microtubules and neurofilaments
+SCb (slow component b) - enzymes, actin, clathrin
2) intermediate (50-100mm per day): mitochondria and other membrane bound organelles
3) fast (400mm per day): utilizes microtubule motors, synaptic vesicles and neurotransmitters
Retrograde:
- axon toward cell body
- utilizes dynein
- carries endocytosed materials and recycled proteins
- rate -> 100-300mm/day
137
What, in general, are glial cells?
- non-neuronal cells typically derived from embryonic neural crest tissue (except microglia)
- glial cells serve in various support functions in the CNS and PNS
- capable of cell division under appropriate conditions
138
What are the different types of glial cells?
- astrocytes
- oligodendrocytes
- Schwann cells
- microglial cells
- ependymal cells
139
What are astrocytes? What are the two different types of astrocytes?
- derived from neural crest
- only in CNS
- numerous processes with expanded feet (pediceles) that terminate on capillaries or the pia mater
1. fibrous astrocytes:
- found predominantly in white matter
- have long processes with few branches
2. protoplasmic astrocytes:
- predominantly in gray matter
- have shorter processes with many short branches
140
Function of astrocytes?
- regulate composition of intercerllular environment or entry of substances into it
- structural support
- blood-brain barrier (mediate exchange of nutrients and metabolites between brain and neurons, end feet form glia limitans)
- development of cerebral cortex
- potassium sink
- secretion of neuron trophic factors
- uptake/metabolism of neurotransmitters
- help form noncollagenous scar tissue after injury top CNS
141
What are oligodendrocytes and what is the function?
-derived from neural crest
-found in CNS
FUNCTIONS
-closely associated with neuron cell bodies in gray matter and function as satellite cells
-surround axons of unmyelinated fibers in gray matter
-myelinate axons in CNS (myelinates several axons)
142
What are Schwann cells?
- neural crest cells
| - function: myelinate axons in the PNS (myelinates a single section)
143
What are microglia?
-derived from macrophage precursors (bone marrow)
FUNCTIONS
-phagocytic in PNS
-recruit leukocytes across the blood-brain barrier
-modulate initiation and progression of immune responses along with astrocytes
144
What are ependymal cells?
- ciliated cuboidal cells
- derived from neuroepithelium and line ventricular system of CNS
- function in transport
- in choroid plexus, may be principal cell type that secretes cerebrospinal fluid
145
What are satellite cells?
derived from neural crest
- form crescents around cell bodies in ganglia
- function as insulators
146
How are axons in the PNS myelinated?
- Schwann cell plasma membrane wraps around axon
- Schwann cell cytoplasm is squeezed out, leaving behind concentric layers of membranes
- internal and external mesaxon: outer and innermost points of fusion between and outer leaflets
147
What are the different structures one will find in a myelinated axon? (when forming)
-internal and external mesaxon: outer and innermost points of fusion between and outer leaflets
-intraperiod line: electron dense line created by extracellular space between adjacent outer leaflets
-major protein zero is a transmembrane protein that forms homodimers
+only in PNS
+homodimers form homotetramerrs with the opposing outer leaflets
+cytoplasmic domains may have signaling functions
+mutations related to Charcot-Marie-Tooth disease
+in CNS protein is replaced by the proteolipd protein which has four homophobic domains. Mutations result in Pelizaeus-Merzbacher disease
-major dense line: electron dense line created by cytoplasmic space remnant between adjacent inner leaflets
myelin basic protein is associated with inner leaflets
+function to stabilize lipids in leaflet
+number of forms created by splicing single gene
-Schmidt-Lanterman cleft (incisure): residual area of cytoplasm within the major dense lines
148
What are the components of a synapse?
-presynaptic membrane
+calcium voltage gated channels
+SNAPs bind synaptic vesicles to presynaptic membrane (soluble NSF)
+vesicle docking proteins (SNAP receptors found in presynaptic and synaptic vesicular membranes)
+synapsins: filaments in the presynaptic membrane
Postsynaptic membrane:
-neurotransmitter receptors
149
What are the different types of synapses?
- axosomatic (terminates with neuron cell body)
- axoaxonic (terminates with another axon terminal)
- axodendritic (terminates with a dendrite)
- axospinous terminates with dendrite spine)
- excitatory (more positive end plate potential -> closer to threshold)
- inhibitory (more negative end plate potential -> further from threshold)
150
What holds the Schwann cell together in the CNS vs PNS?
PNS: myelin protein zero
CNS: proteolipid protein
151
What tissues compose the neural tube and where are they found?
```
-pseudostratified epithelium
+ventricular zone
+intermediate zone (area of destruction of excess neurons via apoptosis)
-cortical plate (mantle layer)
+postmitotic neurons
+future gray matter
-marginal layer
+axons
+future white matter
```
152
What are the characteristics of nervous tissue?
- irritability: specialized to receive stimuli
- conductibility: specialized to transmit impulses
- cellular components -> neurons and neuroglial cells
153
Components and characteristics of a cell body.
- nucleus
- Nissl bodies consisting of RER and free ribosomes
- extensive RER visible with light microscopy and elaborate Golgi structures
- abundant mitochondria
- abundant neurotubules and neurofilaments
- lipofucsin granules are formed from lysosomes and accumulate with age of the neuron
- associated with ligand gated channels and local potentials
154
Components and characteristics of dendrites.
- conduct impulses (local potentials) toward cell body
- contain Nissl substance, mitochondria -> no Golgi
- may be studded with dendritic spines
- tend to taper distally and may branch
- associated with ligand gated channels and local potentials
155
Components and characteristics or axon hillock.
- site for the origin of he axon
- devoid of Nissl substance
- associated with AP generation
156
Components and characteristics or axon.
- voltage gated cation channels and AP
- contain mitochondria and microtubules
- lacks RER, ribosomes, and Golgi
- constant diameter entire length
- terminates in branching telodendrites
- telodendrites contain vesicles and related proteins
- telodendrites form the presynaptic membranes
- may be enclosed within a myelin sheath
157
How can neurons be classified?
- function
- processes
- length of axon
158
What are the different types of neurons according to function?
- sensory (afferent)
- motor (efferent)
- interneurons: transmit impulses within CNS and between sensory and motor neurons
159
How are neurons classified according to morphology?
- multipolar neurons: most common, single axon and multiple dendrites
- bipolar: two processes, one at each end of the spindle shaped neuron. associated with special senses
- pseudounipolar: single process from cell body that bifurcates into a central and peripheral process, found in ganglia along side spinal cord (dorsal root ganglia)
160
How are neurons classified according to axon length?
- Golgi I: neurons with long axons that leave gray matter
| - Golgi II: neurons with short axons that stay within gray matter
161
Difference between an nerve and tract.
nerve: bundle of axons in PNS
tract: bundle of axons in the CNS
162
Difference between ganglion and nucleus.
ganglion: aggregation of cell bodies and dendrites in PNS
nucleus: aggregation of cell bodies and dendrites in CNS
163
Characteristics of epineurium.
- thick fibrous coat
- covers entire nerve
- supplied by blood and lymphatic vessels
- type I collagen and fibroblasts
164
Characteristics of perineurium.
-dense CT
-covers bundles of axons (fascicles)
-epithelial like fibroblasts on inner surface are joined by tight junctions
+zona occludens
+permeability barrier
+has to be rejoined during microsurgery
-blood nerve barrier
+endothelial cells of vessels are also linked by tight junctions
165
Characteristics of endoneurium.
- thin layer of reticular CT
- surrounds individual fibers and Schwann cells
- type III collagen
166
What are the different types of synapses?
axosomatic-axon terminal synapses with the neuron cell body
axoaxonic- axon terminal synapses with another axon terminal
axodendritic- axon terminal synapses with dendrite
axospinous- dendritic spine
excitatory- more positive end plate potential
inhibitory- more negative end plate potential
167
List the meninges and spaces from superficial to deep.
- pia mater
- arachnoid trabeculae
- arachnoid with villi
- subdural space with venous sinus
- dura mater
- epidural space
- bone
168
Characteristics of dura mater.
-tough sheet of dense fibrous CT
169
Characteristics of arachnoid mater.
- composed of delicate CT
- outer -> subdural space and composed of arachnoid barrier cells
- connected to pia via arachnoid trabeculae
- spaces between arachnoid and pia is subarachnoid space and filled with CSF
- arachnoid villi (barrier cells) extend from the outer surface of arachnoid into overlying venous sinuses to dura mater and allows flow from subarachnoid to dural space
170
Characteristics of pia mater.
- follows contours of brain and dips into sulci
- continuous with perivascular CT of brain and spinal cord blood vessels
- tightly attached to nervous tissue and cannot be removed without damaging it
- perivascular spaces are tunnels covered with pia mater
171
What is the choroid plexus?
- highly infolded simple cuboidal epithelium that extends into the ventricles from the roof plate
- linked by tight junctions that form CSF barrier
- active transport
- fenestrated capillaries
- pump fluid into ventricular lumen causing a flow of water, solutes, and proteins from capillaries into ventricles
172
What is the ependyma?
- simple cuboidal epithelium that lines ventricular walls
- linked by zonula adherens adn have microvilli, cilia, and microvilli
- contact astrocytic processes -> glia limitans
- secrets CSF
173
Dorsal root ganglia (sensory)
-capsule of CT (epineurium)
-clustered pseudounipolar neurons lies within the capsule
-myelinated postganglionic axons
-satellite cells
+similar to Schwann cells and derived from neural crest
+form single layer around the cell body of each neuron
+in contact with basal lamina
174
Autonomic ganglia
- capsule of epineurium
- clustered multipolar neurons -> receive input from myelinated preganglionic neurons
- post are not myelinated
- satellite cells are less numerous
175
What are the three covering of the eye?
```
-fibrous tunic
+sclera (tunica fibrosa)
+cornea
-vascular tunic
+choroid
+ciliary body
+iris
-inner tunic
+retina
```
176
What are the layers of the fibrous tunic of the sclera?
-episcleral layer
+outer layer
+loosely arranged collagen and elastic fibers
+highly vascular
+attaches the lining of the eyelid (conjuctiva) to the sclera
-sclera proper
+made up of interlacing collagen fibers
+attachment site for tendons of extrinsic eye muscles
+collagen bundles are always parallel to outer surface of sclera
-lamina cribosa
+perforated disc of sclera
+pass through for optic nerve fibers
177
How are the sclera and cornea related?
- anteriorly sclera is continuous with the cornea
- junction between the two is the limbus -> highly vascular
- posteriorly the sclera is continuous with the dural covering of the optic nerve
178
What are the layers of the fibrous tunic of the cornea?
-corneal epithelium
+stratified, nonkeratinized spuamous epithelium (5-6 layers)
+highly mitotic in basal layer (turnover= 1 week)
-Bowman's membrane
+acellular layer separates epithelium from stroma
+randomly arranged collagen fibers
-corneal stroma
+thin layers of ordered arrays collagen fibers
-descemet's membrane
+acellular layer of collagen bundles
+separates stroma from endothelium
-corneal endothelium
+single layer of large squamous cells
179
What is the difference between anterograde and retrograde transport?
```
anterograde:
-cell body toward distal end of axon
-utilizes kinesin
-rate of transport:
+slow(1-6mm/day), two systems:
>SCa (slow component a)
>preassembled microtubules and neurofilaments
>SCb (slow component b)
>enzymes, actin, and clathrin
+intermediate (50-100mm/day)
>mitochondria and other membrane bound organelles
+fast (400mm/day)
>synaptic vesicles and neurotransmitters
```
Retrograde:
- axon toward cell body
- utilizes dynein
- carries endocytosed materials and recycled proteins
- rate of transport (100-300mm/day)
180
What are glial cells?
- glial cells are non-neuronal cells typically derived from embryonic neural crest tissue (except microglia)
- serve in various support functions in the PNS and CNS
- capable of cell division under appropriate conditions
181
What are the different types of glial cells?
- astrocytes
- oligodendrocytes
- Schwann cells
- microglial cells
- ependymal cells
182
What are some characteristics of astrocytes?
- derived from neural crest
- only in CNS
- numerous processes with expanded feet (pediceles) that terminate on capillaries or the pia mater
- fibrous astrocytes: white matter, long processes and few branches
- protoplasmic astrocytes: gray matter, shorter processes with many short branches
183
What are the functions of astrocytes?
-regulate composition of intercellular environment or entry of substances into it
-structural support
-blood-brain barrier
+mediate exchange of nutrients and metabolites between blood and neurons
+end feet form glia limitans
-development of cerebral cortex
-potassium sink
-secretion of neuron trophic factors
-uptake/metabolism of neurotransmitters
-help from noncollagenous scar tissue after injury to CNS
184
What are the characteristics and functions of oligodendrocytes?
-derived from neural crest
-CNS
Functions:
-closely associated with neuron cell bodies in gray matter and function as satellite cells
-surround axons of unmyelinated fibers in gray matter
-myelinate axons in CNS
185
Characteristics and functions of Schwann cells?
-neural crest
functions:
-myelinate axons in PNS (single section)
186
Characteristics and functions of microglial cells?
-derived from macrophage precursors (bone marrow)
functions:
-phagocytic in PNS
-recruit leukocytes across blood-brain barrier
-modulate initiation and progression of immune responses along with astrocytes
187
What are ependymal cells?
- ciliated cuboidal cells
- derived from neuroepithelium and line ventricular system of CNS
- transport
- in choroid plexus, may be principal cell type that secretes CSF
188
What are satellite cells?
- derived from neural crest
- form crescents around cell bodies in ganglia
- function as insulators
189
How are axons in the PNS myelinated?
- Schwann cell plasma membrane wraps around axon
| - Schwann cell cytoplasm is squeezed out leaving behind concentric layers of membrane
190
What are structures of a myelinated axon can be seen under an electron microscope?
-internal and external mesaxon:
+outer and innermost points of fusion between the outer leaflets (extracellular)
-intraperiod line:
+electron dense line created by extracellular space between adjacent outer leaflets -> major protein zero is a transmembrane protein that forms homodimers (PNS), signaling function
-major dense line:
+electron dense line created by cytoplasmic space remnant between adjacent inner leaflets
+myelin basic protein is an abundant protein associated with the inner leaflets -> stabilize lipids and forms created by splicing a single gene
-Schmidt-Lanterman clefts:
+residual areas of cytoplasm within the major dense lines
191
What are the components of a synapse?
-voltage gated calcium channels
-SNAPs bind synaptic vesicles to membrane
+soluble NSF -> cytosol of terminal
-vesicle docking proteins
+SNAP receptors found in presynaptic and synaptic vesicular membranes
-synapsins
+filaments in the presynaptic membrane
192
What are the layers of vascular tunic (uvea)?
- choroid
- ciliary body
- iris
193
What are the characteristics of the choroid?
-extends anterior to ora serrata of the retina
-highly vascularized with loose CT
+forms choriocapillary network -> contains small blood vessels that supply cells of the retina
+provides nutrients to the retina
+consists of medium and large arteries and veins as well as a wide-bore capillary network
+melanocytes
-Bruch's (glassy) membrane
+acellular fused basal laminae of choriocapillaires and pigmented retinal epithelium
194
What are the characteristics of the ciliary body?
-wedge shaped expansion of choroid peripheral to the lens
-covered by a double layer of cells
+innermost layer is continuous with the pigmented layer of the retina
+surface layer is from the sensory layer of the retina
+produces aqueous humor
-suspensory ligaments (of Zinn) extend to just behind lens equator and anchor the lens in place
-ciliary muscles
+smooth muscle that changes the shape of the lens
+innervated by parasympathetic neurons
195
How do the ciliary muscles contract for accommodation?
close vision (lens thickens):
- ciliary muscle contracts
- ciliary body with inserted zonular fibers moves closer to the lens
- tension is reduced and the lens rounds up
distant vision (lens thins):
- ciliary muscle is relaxed
- ciliary body with inserted zonular fibers moves away from the lens
- the tension of the zonular fibers increases and the lens flattens
196
How does the ciliary body produce aqueous humor?
-nonpigmented surface layer of cells produces aqueous humor
+basal infoldings
+secrete aqueous humor into posterior chamber
+aqueous humor:
>percolates through trabecular meshwork
>flows into canal of Schlemm
197
What are the characteristics of the iris?
-located anterior to the lens and separates and the anterior and posterior chamber
-angle -> formed at lateral borders of the anterior chamber, loose CT, part of the passageway for aqueous humor
-surrounds pupil
-double layer of epithelium
+inner layer -> pigmented epithelial cells
+outer layer of radially oriented myofilaments
>dilator pupillae muscle
>sympathetic innervation
>dilates pupil
+concentric layer of the myofilaments
>constricts pupil
>parasympathetic innervation
-melanocytes (the more melanocytes, the darker the color)
198
What structure is part of the inner tunic?
retina
199
What are the structures that can be found on the retina?
```
-optic disc
+where optic nerve exits
+has no photosensitive qualities and is known as the blind spot
-fovea centralis
+2.5mm lateral to optic disc
+yellow pigment -> macula lutea
+contains only cones
+area of most acute vision
```
200
What divides the inner tunic? What lies anterior and posterior?
-ora serrata divides inner tunic
- posterior lies the photosensitive region
- anterior consists of iris, ciliary body, and ciliary processes
201
Describe the path the aqueous humor takes.
1. produced by epithelial lining of ciliary processes
2. flows from post chamber through pupil into anterior chamber.
3. canal of Schlemm lined by endothelium doesn't communicate with trabecular meshwork. Fluid percolates through thin endothelial lining and loose CT
4. aqueous veins and are collector channels draining the canal of Schlemm into the episceral veins
202
What are the different chambers of the eye?
-anterior chamber (posterior to cornea and anterior to iris)
-posterior chamber (posterior to iris and anterior to lens)
-vitreal chamber posterior to lens)
+contains vitreous body
+gelatinous mass made up of 99% water, hyaluronic acid, vitrein
+hyaloid canal is the site of the fetal artery
203
What is glaucoma?
-increased intraocular pressure due to compromised drainage of aquaeous humor from anterior chamber
204
What are the layers of the retina?
- pigmented epithelium
- inner and outer segments of rods and cones
- external limiting membrane
- outer nuclear layer
- outer plexiform layer
- inner nuclear layer
- inner plexiform layer
- ganglion cell layer
- optic nerve layer
- internal limiting membrane
205
pigmented epithelium
- adjacent to choroid
| - derived from outer layer of the optic cup, outer layer layer of the optic cup
206
inner and outer segments of rods and cones
- outer segment consists of rhodopsin-containing lamellae
| - inner segment consists of areas of rods and cones possessing mitochondria, RER, Golgi, and glycogen
207
external limiting membrane
- area at junction of inner and outer segments of rods and cones and outer nuclear layer
- includes adherens junctions between rods and cones and Mueller cells
208
outer nuclear layer
-cell bodies of rods and cones (first order neurons)
209
outer plexiform layer
-area of synapses between axons of rods and cones and dendrites of bipolar neurons and horizontal cells
210
inner nuclear layer
-cell bodies of bipolar cells (second order neurons), horizontal cells, amacrine cells, and Mueller cells
211
inner plexiform layer
-area of synapses between axons and bipolar cells and dendrites of ganglion cells
212
ganglion cell layer
-cell bodies of ganglion cells (third order neurons)
213
optic nerve layer
-axons of ganglion cells
214
internal limiting membrane
-terminations of Mueller cell processes and their basement membrane
215
What are the different cells that can be found in the retina?
- pigmented epithelial cells
- bipolar cells
- horizontal cells
- amacrine cells
- Mueller cells
- ganglion cells
216
Pigmented epithelial cells
- adjacent to choroid
- synthesize melanin
- apical processes surround and protect outer segments of rods and cones
- phagocytose and degrade lamellae from rods and cones
- connected via tight junctions to form blood-retina barrier
- esterfy vitamin A used in formation of photosensitive pigements
217
Bipolar cells
-condusting neurons that synapse with rods and cones
218
Horizontal cells
-interneurons that interconnect rods and cones with each other and with bipolar cells
219
Amacrine cells
-interneurons that connect ganglion cells and bipolar neurons
220
Mueller cells
- neuroglial cells that extend throughout retina
- form external limiting membrane via zonulae adherens between Mueller and rods and cones
- internal limiting membrane is formed by the basement membrane of these cells
221
Ganglion cells
-conducting neurons whose axons form the fibers of the optic nerve
222
What are the structures found of the retina and what are their characteristics?
```
macula lutea
-yellow region surrounding fovea
-highest visual acuity
fovea centralis
-depression of visual axis
-highest density of cone cells
-lacks rod cells and capillaries
optic disc
-lacks photoreceptors
-point where ganglion cells turn into optic nerve
-"blind spot"
```
223
What are the two different types of photoreceptors?
- rods
| - cones
224
What are the different parts of the photoreceptor?
- spherule (rod) and pedicle (cone)
- cell body (nucleus and short axon)
- inner segment (mitochondria and other organelles)
- outer segment (modified cilium, connected by a stalk to inner segment, site of stacks of discs containing photoreceptors)
225
What are disks?
in rods:
- detach from cell membrane and become free
- constantly renewed in rod cells
- older disks are phagocytosed by surrounding pigmented epithelial cells
in cones:
-disk remains attached to cell membrane
226
Characteristics of rods
- use rhodopsin as photopigment
- sensitive to low light intensity
- responsible for black and white vision
- lamellae of outer segment are not continuous with plasmalemma
- axons up to 100 rods synapse with single bipolar body
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Characteristics of cones
- use three different kinds of iodopsins as photopigment
- sensitive to high intensity
- greater visual acuity than rods
- lamellae of outer segment are continuous with plasmalemma
- each cone cell synapses with a single bipolar cells
228
What is a rhodopsin?
- transmembrane glycoprotein
| - consists of opsin and 11-cis-retinal (vitamin A derivative)
229
What events occur when a photon strikes the 11-cis-retinal?
- cis-retinal transforms into 11-trans-retinal
- rhodopsin becomes activated
- activated rhodopsin interacts with trasnducin (G-protin
230
What is bleaching and how to the eyes recover from it?
-disassembly of rhodopsin into opsin and retinal after light stimulation
Regeneration of photopigments:
- 11-trans-retinal is converted back into 11-cis-retina;
- 11-cis-retinal is transported back to photoreceptor
- recombines with opsin
- rhodopsin is regenerated
231
Histology of the lens? (capsule, anterior epithelium, lens nucleus)
capsule:
-insertion point for suspensory ligaments
-glycoproteins and type IV collagen
-secreted by subcapsular epithelial cells
anterior epithelium:
-simple cuboidal epithelium
-give rise to cells that become "lens fibers"
lens nucleus:
-composed of lens cells that mature into fiber-like structures:
+devoid of nucleus and organelles
+filled with crystalline protein
232
Histology of eyelid.
anterior surface:
-covered with skin
-glands of Zeiss (sebaceous glands)
-glands of Moll (sweat glands, ducts open up to eyelash follicles
palpebral fascia:
-fibrous core of eyelids
-Meibomian glands (tarsal)
+sebaceous glands not associates with hair follicles
+open in front of free edge of eyelid
+secretion keeps normal tear film in eye
palpebral conjunctiva
-stratified columnar or squamous epithelium with goblet cells
-lines inner surface of eyelid
-continuous with bulbar conjunctiva (covers eyeball)
233
What is secreted from the lacrimal gland?
- lactoferrin (bacteriostatic agent)
- lysozyme (bacteriolytic agent)
- secretory immunoglobin A (defensive agent)
- tear specific prealbumin
234
Outer ear structures and characteristics.
auricle:
-pinna and auditory canal
-integumentary overlying elastic cartilage
+thin, keratinized stratified squamous
+hair follicles can be observed in dermis
external auditory meatus:
-outer third of the ear canal composed of elastic cartilage
-inner two thirds is composed of bone
-lining of ear canal is stratified squamous epithelium with serbaceous glands and ceruminous glands
tympanic membrane:
-separates external canal from middle ear
-core is formed from vascularized, innervated CT
-external surface is covered by thin skin
-internal surface is covered by simple cuboidal epithelium
235
What are the ossicles found in the middle ear?
```
malleus:
-hammer
-attached to tympanic membrane
-articulates with anvil
incus (anvil):
-intermediate bone between stapes and malleus
stapes:
shaped like a stirrup
-inserts into oval window
```
236
tympanic cavity structures and characteristics.
```
oval window
-stapes attaches
-opens into scala vestibuli
round window:
membrane covered region at the end of the scala tympani
tensor tympani:
-inserts on malleus
stapedius:
-inserts on stapes
*these muscles contract reflexively in response to loud sounds in order to dampen the vibrations of the auditory ossicles*
```
237
What structures are found in the inner ear?
- bony labyrinth
- membranous labyrinth
- vestibular organ
- auditory organ
238
Bony labyrinth
-complex system of canals and chambers embedded in the petrous portion of the temporal bone
-filled with high sodium perilymph
-consists of:
+semicircular canals
+cochlea
+scala vestibuli
+scala tympani
239
Membranous labyrinth
- complex system of membranous structures embedded within the chambers of the bony labyrinth
- filled with potassium high endolymph
240
Vestibular organs
-patches of sensory structures that respond to changes in position
-consist of:
+maculae of the saccule and utricle
+cristae ampullaris of the semicircular canal
241
Maculae of saccule and utricle
epithelium:
-columnar supporting cells
-vestibular hair cells
+numerous stereocilia
+single kinocilium
-hair cells are in contact with afferent nerve ending
otolithic membrane:
-gelatinous layer containing CaCO3 crystals called otholiths and overlie epithelium
-stereocilia of the vestibular hair cells are embedded in this gelatinous layer
-movements of the head displaces the otolithic membrane and causes a sensory impulse
242
cristae ampullares of semicircular ducts
-epithelium
+columnar supporting cells
+hair cells -> similar to maculae
-cupula
+gelatinous layer similar to the otolithic membrane but without the osoliths
+movement of the head creates shear forces between the semicircular canals and contained fluid
+movement of the fluid displaces the cupula and causes the stereocilia to bend
243
What does the auditory organ consist of?
```
-cochlear duct
+scala vestibuli
+scala tympani
+vestibular membrane
+basilar membrane
+stria vascularis
-organ of Corti
```
244
What does the cochlear duct (scala media) divide the bony cochlea into?
- scala vestibuli
| - scala tympani
245
Where does the vestibular membrane lie?
forms the roof of the duct
246
Where does the basilar membrane lie?
forms the floor of the duct
247
What does the stria vascularis form?
- lateral aspect of the duct
| - formation of endolymph
248
Where does the organ of Corti lie?
-lies on the basilar membrane
