lecture 12 - cartilage histology Flashcards
What are the 3 key components of connective tissue?
Cells, fibres, ground substance
What does the ‘chondro-’ suffix relate to?
cartilage
What is subchondral bone?
Bone that lies underneath a layer of cartilage
What are the features of a protein forming cell?
Has more rough ER, a euchromatic nucleus and a prominent nucleolus.
What does the suffix ‘-blast’ relate to?
Precursor cells
What does the suffix ‘-cyte’ relate to?
Mature cells
What are the 2 broad categories of connective tissue?
Irregular, regular
What are the 3 key structures that are made up of regular connective tissue?
fascia & aponeurosis, ligaments, tendons
What are the 3 types of irregular connective tissue?
Loose CT, Dense irregular CT, adipose tissue
What is the most abundant type of irregular connective tissue?
Loose - LFCT
What are the 2 key components of the extracellular matrix of connective tissue?
Fibres, ground substance
What are the 2 fibre types found in connective tissue?
collagen, elastin
What are the 3 key protein types found in the ground substance of connective tissue?
glycosaminoglycans, proteoglycans, hyaluronan
What are the 2 classes of cells found in the connective tissue?
Resident cells, migrant cells
What are the resident cells of connective tissue?
Cells that are locally residing and of mesenchymal origin
What is the origin of resident cells in the connective tissue?
Mesenchymal origin
What is mesenchymal origin?
Cells that are derived from the mesoderm of the early embryo, including connective tissue cells
What are the 3 key types of resident cells in connective tissue?
fibroblasts, adipocytes, mesenchymal stem cells
What are migrant cells in connective tissue?
connective tissue cells produced in bone marrow that migrate through capillaries to the connective tissue
What is the origin of migrant cells in the connective tissue?
hemopoietic
What are the 3 key types of migrant cells in the connective tissue?
mast cells, macrophages, lymphocytes
What are mesenchymal stem cells?
Cells that can later differentiate into necessary cells types, such as connective tissue cells
What is the shape of adipocytes?
oval or spherical
What are adipocytes filled with?
Droplets of fat
What is the position of the cytoplasm and nucleus of an adipocyte?
On the peripheral rim
What is the most numerous type of connective tissue resident cell?
Fibroblast
What is the shape of fibroblasts?
Fusiform/spindle shaped
What do fibroblasts usually adhere to in connective tissue?
fibres - collagen or elastin
What is the function of fibroblasts?
Produce extracellular matrix in connective tissue
What are the organelle features of fibroblasts, and why?
Adapted for high protein synthesis to produce ECM, so have large euchromatic nucleus, prominent nucleolus, abundant rER and mitochondria
What is the shape of mast cells?
Round or oval shaped
What is the position of the nucleus of a mast cell?
Central
What are the organelle features of mast cells?
Prominent vesicles/granules, prominent golgi, little ER
What do the granules of mast cells often contain?
histamine, heparin
Under what cirumstances will mast cells release their granules?
Trauma, antigen
What is the single unit of a collagen fibre?
Alpha helix
What are the intermediates in the formation of a collagen fibre from alpha helix units?
1.) alpha helix
2.) triple alpha helix
3.) tropocollagen
4.) collagen fibril
5.) collagen fibre
What is the structure of elastin fibres?
single elastin molecules cross linked by link proteins
What is the colour of unstained collagen?
White
What type of strength does collagen have?
mechanical
What is the relative orientation of collagen fibres within connective tissue?
run parallel as bundles
What is the most common type of collagen?
Type 1
Where is type I collagen typically found?
dermis, bone, tendons, ligaments
Where is type 2 collagen found?
Cartilage
Where is type 3 collagen found?
Dermis
Where is type 4 collagen found?
Basal lamina
What is the nature of elastin fibres undergoing stress/strain?
Stretch and recoil easily
What are the 2 key components of proteoglycan monomers in ground substance?
GAGs (glycosaminoglycans), core protein
Why must proteoglycan monomers be linked by hyaluronan in the ground substance?
Because the monomers are negatively charged and would repel if not linked together
How are proteoglycan monomers connected to hyaluronan?
Via link proteins
What structure acts as a backbone for proteoglycans monomers to bind to forming a proteoglycan polymer?
Hyaluronan
What connects proteoglycan polymers in the ECM?
Collagen and elastin fibres
What structure covers cartilage, except at articular surfaces of synovial joints?
Perichondrium
What are the 3 key types of cartilage?
Hyaline cartilage, white fibrous cartilage, yellow elastic cartilage
What are the 2 types of growth that result in the formation of cartilage?
Appositional growth, interstitial growth
At what part of the cartilage does appositional growth occur?
The perichondrium
What cells at the perichondrium generate appositional growth of cartilage?
Chrondrogenic cells/young chondroblasts
At what life stage does interstitial growth of cartilage occur?
very early age
What cellular process causes interstitial growth of cartilage?
Mitotic division of existing cartilage cells
What is the function of chondroblasts?
Synthesise extracellular matrix in cartilage
Which cells synthesise extracellular matrix in cartilage?
Chondroblasts
What do the daughter cells of dividing chrondoblasts form?
Chondron/cell nest
What are individual chondroblasts contained within inside cell nest of four cells?
A lacuna
What is the thick layer that surrounds a cell nest in growing cartilage?
Territorial matrix
What is the thin layer that surrounds the cell nest in growing cartilage?
Inter-territorial matrix
What is the difference between chondroblasts and chondrocytes?
Chondroblasts are immature, then mature to become chondrocytes. Chondroblasts produce ECM, while chondrocytes maintain the cartilage
What is the function of chondrocytes?
Maintain the cartilage matrix
What changes occur as chondorcytes mature?
Less active in producing matrix, so nucleus is heterochromatic, nucleolus is smaller, reduced protein machinery.
What are the 2 GAGs found in the proteoglycan monomers within the ECM of cartilage?
Chondroitin sulphate, keratan sulphate
What type of cartilage has the most cells, and little fibres?
Hyaline/articular cartilage
What type of cartilage has a lot of both types of fibres?
(white) fibrocartilage
What type of cartilage has the highest concentration of elastin fibres?
Yellow elastic cartilage
What is the arrangement of cells in hyaline/articular cartilage viewed histologically?
In cell nests/chondrons with 2-4 cells
What is the nature of the ECM of hyaline/articular cartilage?
lots of ground substance, lack of collagen, rich in proteoglycans
What type of collagen is present in Hyalin Cartilage?
Type II collagen
What is the relationship between loading on the joint and the thickness of articular cartilage?
There isn’t one, thickness does not increase in relation to increased load
What are the 4 zones/layers in articular cartilage, from superficial to deep?
1.) superficial zone
2.) intermediate zone
3.) radial zone/deep
4.) calcified zone
What is the nature of cells in the superficial zone of hyaline cartilage?
Small, elongated, parallel to surface
What is the nature of collagen in the superficial zone of hyaline cartilage?
Fibrils arranged tangentially to surface
What is the nature of cells in the intermediate zone of hyaline cartilage?
Large and round
What is the nature of collagen in the superficial zone of hyaline cartilage?
Obliquely oriented
What is the nature of cells in the radial/deep zone of hyaline cartilage?
cells arranged vertically in rows
What is the nature of collagen in the radial/deep zone of hyaline cartilage?
Fibres arranged perpendicularly
What is the contents of the calcified zone of articular cartilage?
Calcified cartilage
What histologically significant boundary separates the deep and calcified zones of hyaline cartilage?
Tide mark
What is the function of white fibrocartilage?
Load bearing - resist high compressive forces due to high collagen content
What type of collage does white fibrocartilage have?
Type I
What is the arrangement of cells in white fibrocartilage?
Rows of chondrocytes within lacuna lined between collagen fibres
What is the arrangement of fibroblasts in white fibroblasts in white fibrocartilage?
Randomly placed
What is the arrangement of cells in yellow elastic cartilage?
Either single OR in groups
What type of collagen is found in yellow elastic cartilage?
Type II
What supplies blood to cartilage?
No blood supply - avascular
How does cartilage receive nutrition and metabolites without a blood supply?
Via diffusion from vessels of synovial membrane and hypochondral vessels.