Connective Tissue Flashcards
5 types of mesenchymal cells
• fibroblast - fibrocyte
• chondroblast - chondrocyte
• osetoblast - osteocyte
• adipocyte (white/ brown adipose tissue)
• mast cells
5 types of haematopoetic cells
• monocytes
• macrophages
• lymphocytes
• mast cells
• Blood Cells
Collagen
tropocollagen is a triple helix of peptides -about 300nm long
• Fibroblasts secrete tropocollagen subunits
• Fibres assembled extra-cellularly
• More than 20 types
Variable thickness and length, often run in bundles
• Neither elastic nor contractile
• Most forms only produce linear fibres
Type I collagen
Skin
Type II collagen
Cartilage
Type III collagen
Liver, spleen, bone marrow
Type IV collagen
Basement membrane
Type V collagen
Placenta
Loose connective tissue
comprises of widely spaced thin collagen fibres, fibroblasts/fibrocytes, unstained ground substance
Dense connective tissue
comprises of: closely spaced thick collagen fibres, fibroblasts/fibrocytes, unstained ground substance
• May be irregular or regular
All collagen fibres run in same orientation
Example of dense connective tissue
Tendons and ligaments
Reticulin
type III collagen
• Fibrillar collagen
• Forms a supporting scaffold in many organs eg bone marrow, liver, kidney, lymph node, spleen
• Not visible with H&E- need a silver stain (the black lines)
• Can form branched fibres
Elastin
elastic tissue contains fine fibres and sheets of elastin
• Fibres may be branched
• Produced by fibroblasts
• Stain pink with H&E- more clearly visible with Van Gieson
• Easily confused with smooth muscle cells
• Important in blood vessels as allows recoil and stretch
White adipose tissue
large cells with single fat globule in each cell that pushes cytoplasm and nucleus to edges
• Usually appear empty in conventional slides as fat is extracted during processing
• Protect vital organs, insulation and serve as energy stores
Where is white adipose tissue normally found
eg around aorta, kidneys, in subcutis, omentum
Brown adipose tissue
cells with many globules of fat (multi-locular)
• Important in neonatal thermo-regulation (generate heat via oxidation of fatty acids) as have a high SA:VOL
Disappear with age
Where is brown adipose tissue found
Found across shoulders and down back of newborn, on chest between shoulder blades
Cartilage
hard connective tissue
• Constituents:
• Cells- chondroblasts, chondrocytes (appear in clumps)
• Extracellular matrix - glycosaminoglycans (hyaluronic acid), proteoglycans (condroitin sulphate, keratin glycan) = flexible, compressible and hardwearing
• Extracellular fibres- collagen, elastin
• Cartilage is avascular- received nutrients and oxygen via diffusion from surroundings
• Surrounded by a fibrous capsule (collagen)- Perichondrium
3 types of cartilage
Hyaline, fibrocartilage and elastic cartilage
Hyaline cartilage
found in synovial joints (knee joint, nasal septum)
• Chondrocytes in lacunae surrounded by a glassy amorphous matrix
• No visible fibres
• Perichondrium- fibroblasts and collagen
Matrix bonds large amounts of water which, when impressed, exudes from cartilage before being taken up again when pressure is released
Fibrocartilage
found in the annulus (intervertebral discs), fibrosis, pubic symphysis
• Visible collagen fibres in matrix
• Perichondrium- fibroblasts and collagen
Elastic cartilage
found in the pinna (ear), epiglottis
• Visible elastic fibres in matrix
• Perichondrium fibroblasts and collagen
• Visible with H&E but more visible with silver staining
Synovium
lines the inside of the joint capsule
• 1-4 layers of synovial cells
• Type A- phagocytes
• Type B- rich in RER and secrete synovial fluid
• variable shapes- squamous to cuboidal
• Richly vascular, highly innervated
3 muscle types
Smooth muscle, skeletal muscle, cardiac muscle
Smooth muscle
involuntary muscle
• discrete Fusiform cells coupled together by gap junctions so they function as a whole
• Each gap junction consists of a complex of 6 connexon proteins that span the cell membrane linking the interiors of adjacent muscle cells
• Guarded central pore in the connexon complex permits small molecular weight molecules (signal molecules) to passs from one cell to the next in the chain, electrically coupling and allowing the cotraction stimulus to pass from one cell to the next quickly
• Not individually innervated so contract slower than skeletal muscle fibres as rely on a stimulus arriving via a gap juction
• Anchored focally to inside of cell membrane
• Central oval or flattened nucleus
• Have several surface receptors to allow response to hormonal stimuli
• No striations
• non-branching, elongated spindle shapes
Where is smooth muscle found
Found in walls of blood vessels, tube of intestine, bronchioles of lung, uterine wall (myometrium)
Is smooth muscle striated
No
Does smooth muscle have branching
No
Where is the nucleus
Central
Is cardiac muscle striated
Yes
Is cardiac muscle branching
Yes
Where is the nucleus in cardiac muscle
Central
Is skeletal muscle striated
Yes
Does skeletal muscle have branching
No
Where is the nucleus in cardiac muscle
The edge
Visible extracellular fibres
Collagen, elastin, reticulin
Invisible extracellular fibres
Fibronectin and laminin
Ground substances
Glycosaminoglycans and proteoglycans
Which tissue lacks lymphatics
Cartilage
Why is articular cartilage slow to repair
Articular cartilage doesn’t have a fibrous perichondrium. Perichondrium is a rich source of chondroblasts for synthesis and repair of cartilage so articular cartilage is slow to repair
Where is hyaline cartilage found
Articular surfaces, supporting rings of trachea and cartilage of larynx.
All long bones initially hyaline cartilage which is subsequently replaced by bone by process of endochondral ossification
Ligaments
thick ribbons of parallel collagen fibres, between which lie the fibroblasts that synthesise them. The fibres become very compact and regular, squashing the fibroblasts
Amorphous material (GAS)
high molecular weight, strong hydrophilic and negatively charged polysaccharide polymers that retain water and maintain the rigorous of the cells embedded within them
Where are connective tissue derived from
Mainly derived from undifferentiated mesenchymal cells but also from haematopoetic stem cell line
Fibrin
an insoluble protein that is produced in response to bleeding and is the major component of the blood clot. Fibrin is a tough protein substance that is arranged in long fibrous chains; it is formed from fibrinogen, a soluble protein that is produced by the liver (hepatocytes) and found in blood plasma.
What are osteoclasts derived from
Blood monocytes
Blast
Immature cells
Cytes
Mature cells
Penis
the penis shows a variety of soft connective tissues from loose to dense irregular.
the penis contains threeerectile compartments each of which is surrounded by a capsule of dense irregular connective tissue surrounding and between which is looser connective tissue (fewer fibres).
During an erection, blood fills compartment so it becomes rigid. Becomes flaccid again when blood drains from compartment
Which 2 organs have 3 layers of muscularis propria
Stomach
Bladder
Which 2 organs have no muscularis mucosa
Gallbladder
Ureters
Structure of type IV collagen
Non-fibrillar
