Histology and Physiology Flashcards
Describe loose CT
areolar
Elastic fibers and collagen fibers in ground substance. Fibroblasts, mast cells, macrophages and capillaries
In tunica adventitia of blood vessels, muccosa and sub mucosa,
Describe dense regular CT
Found in ligaments, tendons, eyes, fascia
Parallel bundles of collagen fibers separated by linear rows of fibrocytes
Describe dense irregular CT
Dermis layer of skin and submucosa of GI tract
Corse, thick intertwined bundles of collagen fibers
Few fibroblasts
Reticular CT and
Elastic CT: fibers produced by smooth muscle cells to form discontinous lamellae around lumen
Adipocytes are modified ______
fibroblast
What do fibroblasts make?
Spindle-shaped cell and oval nucleus: synthesize and secrete proteoglycyans, glycoproteins, and precursor molecules of collagen and elastin
Type I collagen
Tough guy
Fibrillar
Bone, tendon, dentin
Type II collagen
Hyaline and elastic cartilage
Thinner
Fibrillar
Type III collagen
Reticular lamina of basement membranes
Fibrillar
Type IV collagen
non fibrillar
basal lamina
no bundles
Type V collagen
Fetal amnion and chorion
Muscle and tendon sheaths
What forms elastin in skin and tendons?
Fibroblasts
What makes elastin in elastic cartilage?
Chondroblasts
What makes elastin in blood vessels and respiratory tract?
Smooth muscles
Hypovitaminosis A
Retards growth, reduces width of epiphyseal plate
Hypovitaminosis C
Inhibits matrix synthesis, leads to deformation of epiphyseal plate and scurvy
Vitamin D deficiency
Chondrocytes proliferate but matrix does not calcify properly
Rickets
Describe fibrocartilage
no perichondrium
Chondrocytes in rows
Abundant in collagen I and II
Ground substance has dermatan and chondroitin sulfate
Found in attachments of ligamentns to articuclar surfaces
The outer layer of perichondrium
fibroblasts, collagen I and blood vessels
Fibrogenic cells
Inner perichondrium
Chondrogenic-give rise to chondroblasts and osteoprogenitor cells
Appositional growth
Formss new cartilage on surface of pre-existing cartilage
Occurs within inner layer of pericondrium
Chondrogenic cells - Collagen I
Chondroblasts - Collagen II
Interstitial growth
Takes place within cartilage mass
Chondrocytes divide within lacunae
Increase mass of cartilage
In adults describe cartilage repair
In adults, few chondrocytes are produced
Cartilage usually replaced by dense CT or bone if vascularized
Cranial synostosis
Bone growth instead of cartilage repair
Cell type A
Phagocytic
Contains lysosomes to clear articular cavity of debris formed by friction of articular cartilages
Describe cell type B
Produce synovial fluid
Fluid has hyaluronic acid to increase viscosity
Lubricin to reduce friction
Diaphysis
The shaft
Compact bone surrounds marrow cavity
Epiphysis
Ends of bone
Spongy bone surrounded by thin compact bone
Contains growth plate or epiphyseal plate
The connective tissue lining of the marrow cavity of the bone
endosteum
What are osteons
Haversian systems: unit of sstructure
Osteoprogenitor cells differentiation regulated by what?
BMP and Cbfa1
Cells are resting and capable of differentiating into osteoblasts
Squamous
Differentiation of osteoblasts controlled by what?
Cbfa1, Runx2 and osteocalcin
What directs the differentiation of osteoprogenitor cells into osteoblasts?
Sox9
What do osteoblasts deposit?
Osteoid
What are osteocytes?
mature or differentiated osteoblasts
Maintain bone matrix
Solitary cells, usually flattened or spindle-shaped
Canaliculi
Wht are osteoclasts
Monocyte-macrophage progenitor cells of bone marrow
Located in Howship’s lacunae
Break down mineralized bone
What is the first indicator of osteogenesis?
Cbfa1/Runx2
Describe intramembranous osteogeneis
Occurs on or within fibrous CT
Osteoblasts deposit osteoid
Primary bone formed
Several ossification centers interconnect to form trabeculae
Skull bones and clavicle
Describe endochondral osteogenesis
Bone replaces a pre-existing cartilaginous template
Chondrocytes in cartilage template become isolated by type II collagen
Chondrocytes hypertrophy and produce type X collagen which promotes angiogenesis
Increased blood vessels and promotes calcification
Chondrocytes undergo apoptosis
Primary centers in diaphysis
Secondary in epiphysis
Describe the zones of endochondral osteogenesis
Reserve zone: hyaline cartilage just below epiphyseal cartilage
Proliferation zone: chondrocytes proliferate, vertical stacks
Hypertrophic zone: chondrocytes enlarge, matrix calcifies, angiogenesis
Vascular invasion zone: blood vessels invade osteoprogenitor cells move in
What indicates the edge of a remodeled osteon?
cement line
What is osteoporosis?
More bone resorbed than replaced.
Describe bone fracture repair
Damaged blood vessels clot Die back Death of osteons around break Macrophages remove debris Intense proliferation of osteoprogenitor cells from periosteum and endosteum Osteoblasts for cellular collar Immature bone formed Trabeculae bone unite to form bony callus Woven bone remodeled into lamellar
Osteoarthritis
Bone ends rub together because of thinned cartilage
Rheumatoid arthritis
Swollen inflamed synovial membrane, bone erosion
Cell migration and specification during gastrulation is controlled by what?
FGF8
What is the anterior visceral endoderm?
Expresses genes essential for head formation, several TFs as well as secreted factors cerberus and lefty
What genes are expressed on the side that will be dorsal mesoderm?
Goosecoid which inhibits BMP
Notochord and paraxial mesoderm formed
What is the T gene?
Brachyrury T gene regulates dorsal mesoderm formatioon in middle and caudal regions
Antagonizes BMP
If not there then ->caudal dysgenesis: shortening of embryo
-sacral agenesis, sirenomelia
Summarize roles of FGF8, Lefty and Pitx2 and serotonin in development of laterality
Cells in primitive node secrete FGF8
Expression of nodal on left side only
Shh on left side (activin inhibits Shh on right)
FgF8 induces lefty 2 expression
Nodal and Lefty 2 regulate PITx2 with serotonin
What happens if no serotonin for developing embryo?
Situs inversus, dextrocardia and heart defects
Situs inversus - heart liver, stomach on opposite side
Visceral heterotaxy - unusual degree of symmetry of some thoracic and abdominal organs
Name syndrome: nodal flow is compromised. Respiratory dysfunction, situs inversus, autosomal recessive, infertility in males?
Kartagener syndrome
Disease category when there is defect of neural tube
Rachischisis
- Split notochord
- premature dysjunction
- Non-dysjunction
- neuropores
What wave fails to close if cerebrum does not form properly, not usually viable
Anencephaly
Wave 2
What wave fails for spina bifida?
Wave 1 and 5
Describe the types of spina bifida
Spina bifida occulta - Vertebra does not form all the way around
Spina bifida menigocele - meninges come out
Spina bifida menigomyeloele - meninges and spinal cord
Spina bifida myeloschisis - meniges and spinal cord exposed to outside
What happens if there is a failure of neural tube closure inbetween wave 4 and 1?
Encephalocele
Associated malformation in secondary neurulation is called what?
myelodysplasias
Milder form usually covered by skin: large capiliaries and prominent dimples, telangiectasias
Conus medullaris and filum terminale abnormally attached to defective vertebral column - constant traction
What is another name for embryonic connective tissue?
Wharton’s jelly
In umbilical cord and pulp of developing teeth
Rich in extracellular matrix and stem cells
Not many cocllagen and reticular fibers
