HISTOLOGY AND EMBRYOLOGY Flashcards
Cartilage (6)
- Capable of enduring a great deal of stress
- It has no blood vessels( avascular) and no nerves
- The cartilage consists of cells and extracellular matrix (ECM) by perichondrium
- Matrix cobsists of collagen and elastic fibers embedded in chondroitin sulfate
- Strength is due to collagen fibers
- Resilience is due to chondroitin sulfate
Perichondrium of hyaline cartilage (4)
- Except in articularcartilage of joints, hyaline cartilage is covered by a layer of dense connective tissue called as perichondrium
- Perichondrium is essentiak for growth and maintenance of cartilage
- Perichondrium consists of type 1 collagen and fibroblasts
- Among these fibroblasts, inenr layer of perichondrium are progenştır cells for chondroblasts
growth of cartilage
INTERSTITIAL GROWTH: Growth from chondrocytes within cartilage.
Isogenous group manifacture matrix, pushed away from each other, forming seperate lacunae and thus enlarging he cartilage from within.
APPOSITIONAL GROWTH: growth from undifferentiated cells at the surface of the cartilage or perichondrium.
thw chondrogenic cells in the inner cellular layer of the perichondrium undergo division and differentiate into chondroblasts, which begin to elaborate matrix.
types of cartilage
- hyaline cartilage
- elastic cartilage
- fibrous cartilage
Hyaline cartilage özellikler
- it is avascular
- it consists of chondrocytes surrounded by territorial and interterritorial matrices containing type 2 collagen interacting with proteoglycans
- ıt occurs in the temporary skeleton of the embryo, articular catilage ( ends of long bones, ends of ribs) and the cartilage of the respiratory tract (nose, parts of larynx, trachea, bronci, bronchial tubes.
elastic cartilage özellikleri
- it is avascular
- it is surrounded by perichondrium
- it consists of chondrocytes surrounded by territorial and interterritorial matrices containing type 2 collagen interacting with proteoglycans and elastic fibers
- elastic fibers can be stained by orcein for light microscopy
- it occus in the external ear, epiglottis and auditory tubes.
elastis cartilage examples
- auricle or pinna
- epiglottis
- external auditory meatus
fibrocartilage
- it is generally avascular
- ıt lacks of perichondrium
- it consists of chondrocytes and fibroblasts surrounded by type 1 collagen and a less rigid ECM
- it predominates in the intervertebral disks, articular disk of the knee , mandible, sternoclavicular joints, and pubic symphysis.
cartilage repair
damaged cartilage undergoes slow and incomplete repair, primarily by the activiy of cells int the perichondrium whic invade the injured area and produce new cartilage and this character is not seen in young children
in extensively damaged areas, perichondrium produces a scar of dens connective tissue instead of new cartilage
the poor capacity of cartilage for repair or regeneration is due to its avascular in nature
Bone function
FUNCTİON:
- support and protection for the body and its organs
- a reservoir for calcium and posphate ions
bone is composed of
- support celss (osteoblasts, osteocytes)
- a non-mineral matrix of collagen and GAG’s (osteoid)
- inorganic mineral salts deposited within the matrix
- remodeling cells (osteoclasts)
Osteoid and bone matrix consists of organic ?% and inorganic ?% components
organic 30%, and inorganic 70%
organic bone matrix
type 1 collagen (90%), proteoglycans enriched in chondroitin sulfate, keratan sulfate, hyaluronic acid, noncollagenous proteins.
noncollagenous matrix proteins are osteocalcin, osteopontin, osteonectin, bone sialoprotein.
inorganic bone matrix
inorganic bone matrix is represented predominantly by deposits of calcium phosphate wit the crystalline characteristics of hydoxyapetite.
osteoprogenitor cells
stem cells of bone
osteoblasts
synthesize the organic component of bone matrix(osteoid), mineralice it by depositing calcium and phosphate hydroxies (hydroxyapetides)
osteocytes
inactive osteoblasts trapped in mineralized bone, lie within small cavities. Adjacent cell processes found within canaliculi are connected by gap junctions.
osteoclasts
multinucleate cells, derived from monocytes, erode ineralized bone, localized in Howship’s lacuna
classification of bones
compact bone
spongy or cancellous bone
types of bone on the basis of microscopic organisatiiın of ECM
lamellar bone: typical mature or compact bone
Woven bone: observed in the developing bone
lamellar bone consists of lamellae, largely composed of bone matrix, and osteocyts each occupying a cavit or lacuna with radiating and branching canaliculi.
vascular channels in compact bone
haversian canal
volkman’s canal
lamellar bone displays four distinct patterns
- osteons of Haversian system
- interstitial lamella
- outer circumferential lamellae
- inner cimcumferential lamellae
periosteum: Inner layer
during embryonic period consist of bone-forming cells (osteo-blasts), is the osteogenic layer. In the adult, periosteum contains inactive connective tissue cells that retain their osteogenic potential in case of bone injury.
periosteum: Outer layer
Rich in blood vessels, some of them entering volkman’s canal, and thick anchoring collagen fibers, called Sharpey’s fibers, that penetrate the outer circummferential lamellae in the bone.
endosteum
consists of squamous cells and connective tissue fibers covering the spongy walls housing the bone marrow and extending into all the cavities of the bone, including the Haversian canals.
mineralization of osteoid
- a glycoprotein (osteocalcin) in osteoid binds extracellular Ca ions, leading to a high local concentration.
- The enzyme alcaline phosphatase, which is abundant in osteoblasts increases local ca and po4 concentration.
- Osteoblasts produce matrix vesicles, whic can accumulate Ca and PO4 ions from larger molecules.
selective bone resorbtion
- lysosomal enymes are released by osteoclasts.
- released enzymes hyrdolyse the collagenous protein and GAG’s of the bone matrix.
- the disrupted bone matrix yields up its attached mineral salts.
- local acidic conditions result from the secretion of organic acids such as carbonic, lactic, and citric acids by osteoclasts, break up the hydroxyaptie, releasing soluble Ca and PO4 ions.
- soluble break own products of demineralisation and proteni hydrolysis may be resorbed by the osteoclast by endocytosis.
- osteoclasts resorbtion of bone can be stimulated by parathormone and inhibited by calcitonin.
osteoporosis
both cortical and trabecular bone is thing
old people
paget’s disease
Osteoclasts are very active
autoimmune disease
osteogenesis types
- intramembranous bone formation
2. endochondral bone formation
intramembranous bone formation
most flat bones are formed by this way. ossification is formed on the mesenchymal connective tissue
endochondral bone formation
most long and short bones are developed by this way. this type of ossification occurs in two steps.
- a miniature hyaline cartilage is formed
- the cartilage model continues to grow and serves as a structural scaffold for bone development.
semi-mobile joints (synarthroses) types
- syndesmoses
- synchondroses
- synostosis
syndesmoses
joints between the flat bones of the skull
synchondroses
joints between ribs and sternum
synostosis
ın old age the support tissue forming both syndesmosis and synchondroses replaced bby bone to form rigid immobile joint
mobile joint (diarthroses)
joints that allow free movement between adjacent bones are termed synovial joints.
sciatica
wear and tear on intervertebral disks may lead to degeneration of the annulus fibrosus, with extension of the nucleus pulposus. this results in:
impaired efficiency of the disk as a shock absorber.
expansion of the annulus fibrosus, causing it to bulge.
synovial membane haas 2 types of cells
- type A cells: phagocytosis
2. type B cells: proteim synthesis
synovium
the internal lining of joint capsule is specialized secretory epithelium, the synovium, which produces synovial fluid.
osteoarthritis
old people
calcification of cartilage occurs
rheumatoid arthritis
pain in joint region
autoimmune
skeletal muscle features
myoblasts fuse with each other: myotubes
- produce myofibrils (composed of myofilaments)
muscle fibers parallel to each other
continuous capillaries
muscle fiber
long
cylindrical
multinucleated (peripherally located beneath sarcolemma)
striated
diameter :10-100 um, hypertrophy high
strength of fiber ~ diameter
strength of entire muscle ~ number and thickness of fiber
skeletal muscle is pink- renk due to
rich vascular supply
myoglobin pigments
- oxygen transporting protein
- resemble but smaller than hemoglobin
classification of skeletal muscle
- red
- white
- ıntermediate
vascularization comparison between red and white muscle ffibers
- red muscle fiber rich
- wmf poorer
innervation comparison between red muscle fibers and white muscle fibers
- rmf smaller nerve fibers
- wmf larger nerve fibers
fiber diameter comparison between red and white muscle fibers
- rmf smaller
- wmf larger
contraction comparison beteen red and white muscle fibers
-red mf
slow but repetitive, not easil fatigued, weaker contraction
-wmf
fast, easily fatigued, stronger contraction
sarcoplasmic reticulum comparison between red and white muscle fibers
- rmf not extensive
- wmf extensive
mitochondria comparison between red and white muscle fibers
- rmf numerous
- wmf few
myoglobin comparison between red and white muscle fibers
- RMF RİCH
- WMF POOR
enzyme comparison between red and white muscle fibers
-rmf
rich in oxidative enzymes, poor in adenosine triphosphatase
-wmf
poor in oxidative enzymes, rich in phosphorylases and adenosine triphosphate
epimysium
- covers entire muscle
- dense irregular collagenous connective tissue
perimysium
- collagenous tissue less dense than that of epimysium
- surround bundles(fascicles) of muscle fibers
endomysium
- reticular fibers (intermingle with those of neighboring cells) and an external lamina (basal lamina)
- surrounds each muscle cell (fiber)
small satellite cells
- single nucleus
- regenerative cells
- located in shallow depressions of muscle cell’s surface –share muscle fiber’s external lamina
bands of muscle
A BANDS: dark bands
I BANDS: light bands
H BAND: at the center of a A band, pale area, devoid thin filaments, bisected by a thin M LİNE.
each I band is bisected by a thin dark line: Z DISC (Z LINE)
sarcomere
- region of myofibril between 2 successive Z discs
- contractile unit of skeletal muscle fibers
during muscle contraction
- I band becomes narrower
- H band is extinguished
- z disks move closer
- width of A band remains unaltered
- individual thick and thin filaments do not shorten
- 2 Z disks are brought closer together as thin filaments slide past the thick filaments ( huxley’s sliding filament theory)
Huxley’s sliding filament theory
- thin filaments move toward the center o f saarcomerre
- a greater overlap beteen thick and thin filaments is created
T tubules
sarcolemma is continued within fiber as numerous T tubules ( transverse tubules)
- long tubular invaginations among myofibrils
- in mammalian skeletal muscle, they pass transversely across fiber
- lie specifically in the plane of junction of A and I bands
- branch and anastomose but remain in single plane
- each sarcomere has 2 sets of T tubules
- facilitate conduction of depolarization waves along sarcolemma
sarcoplasmic reticulum
- in close relation with A and I bands and T tubules
- stores intracelluler calcium
- foms a meshwork around each myofibril
- displays dilated cisternae at each A-I junction
2 sarkoplasmic reticulum + 1 T-tubule =
TRIAD
structural organisation of myofibrils
- thick myofilaments
- myosin II - thin myofilaments
- actin
- originate at Z disk
- project toward center of 2 adjacent sarcomeres - in mammalians, each thşck filament is surrounded by 6 thin filaments
structura organization of myofibrils is maintained by
- titin
- alfa actinin
- cap Z
- nebulin
- tropomodulin
muscle contraction and relaxation
- contraction reduces resting length ofmuscle fiber (equal to sum of all shortenings that occur in all sarcomeres)
- strength of contraction of a muscle is a function of the number of muscle fibers that undergo contraction
- huxley’s sliding filament theory: thin filaments slide past the thick filaments during muscle contraction
rigor mortis
- stiffening of joints
- dead cells unable to produce ATP , so dissociation of thick and thin filaments cannot occur
muscle cell membrane
- modified
- forms primary synaptic cleft, occupied by axon terminal
- secondary synaptic clefts ( junctional folds)
- both clefts linedd by basal lamina
- sarcoplasm in vicinity of secondary cleft rich in glycogen, nuclei, riosomes, mitochondria
muscle spindles
- continuously monitor lenght and changes in length of muscle
- encapsulated sensory organ among muscle cells
- 8-10 elongated, modified muscle cells: intrafusal fibers, surrounded by fluid-containing periaxial space, which is enclosed by the capsule
- skeletal muscle fibers surrounding muscle: extrafusal fibers
goldi tendon organs (neurotendinous spindles)
monitor intensity of muscle contraction
epidermis
is a superficial epithelial tissue that is derived from surface embryoiz ectoderm
dermis
the dermis, undelying the epidermis, is a deep layer composed of dense, irregularly arranged connective tissue that is derived from mesenchyme.
primordium of the epidermis
is the surface ectoderm
periderm
cell in surface ectoderm proliferate and form a layer of squamous epithelium , periderm.
the cells of the periderm continually undergo keratinization and desquamation and are replaced by cells arising from the basal layer.
vernix caseosa
protects the developing skin from constant exposure to amniotic fluid containing urine, bile salts, and sloughed cells.
stratum germinavitum
the basal layer of the epidermis becomes th stratum germinavitum, which produces new cells that are displaced into the more superficial layers. By 11 weeks, cells from the stratum germinativum have formed an intermediate layer.
stratum corneum
replacement of the peridermal cells continues until approximatelly the 21st week; thereafter, the periderm disappears and the stratum corneum forms the stratum lucidum.
epidermal ridges
proliferation of cells in the stratum germinativum also produces epidermal ridges, which extend into the developing dermis. these ridges begin to appear in embryos at 10 week and are permanently established by the 17th week. the pattern of epidermal ridges that develops on the surface of the palms of the hands and the soles of the feet is determined genetically, and constitutes the basis for examining fingerprints in criminal investigations and medial genetics.
when is the blood supply of the fetal dermis is well established
by the end of first trimester
gynecomastia
the rudimentary mammary glands in males normally undergo no postnatal development. Gynecomastia refers to excessive development of male mammary tissue.It occurs in most male neonates because ofstimulation of the mammary glands by maternal sec hormones. this efect disappears in a few weeks. during mid-puberty, approximatelly two thirds of males have varying degrees of hyperplasia of the breast. approximately 80% of males with klinefelter syndrome have gynacomastia.
enamel hypoplasia
defective enamel formation causes pits, fissures, or both in the enamel of teeth. these defects result from temporary disturbances of enamel formation. various factors may injure ameloblasts(source of enamel), such as nutritional deficiency, tetracycline therapy, and infectious diseases. rickets arising during the critical period of permanent tooth develpoment is the most common cause of enamel hypoplasia.
rickets
rickets, a disease in children who are deficient in vit D, is characterized by disturbance of ossification of the epiphyseal cartilages and disorientation of cells at the metaohysşs-section of bone between the epiphysis and diaphysis
amelogenesis imperfecta
ın amelogenesi imperfecta, the toth enamel is soft and friable because of hhypocalcification, and the teeth are yellow to brown in color.
macrodontia
macrodontia( a single large tooth) is a condition caused by the union of two adjacent tooth germs.
dentinogenesis imperfecta
dentinogenesis imperfecta is relatively common in Caucasian children. ın affected children, the teeth are brown to gray-blue, with an opalescent sheen. this is caused by failure of the odontoblasts to differentiate normally, producing poorly calcified dentin. both deciduous and permanent teeth are usually involved. the enamel tends to wear down rapidly, exposing the dentin. this defect is inherited as an autosomal dominant trait.
