Define connective tissue
Forms a continuum throughout the body linking muscle, nerve and epithelial tissue in a structural way, but always providing support in metabolic and physical ways
Name the 5 types of connective tissue
1) Fibrocollagenous (loose, dense regular and dense irregular)
What are the main components of connective tissue?
1) Extracellular fibres
2) Amorphous ground substance
3) Cells Organic components only
What are the resident cell types found in connective tissue and their function?
1) Macrophage - ingest foreign material
2) Fibroblasts - Secrete collagen and components of extracellular matrix
3) Mesenchyme - Undifferentiated cells that maintain extracellular matrix
What are the visitant cell types found in connective tissue and their function?
Adipocytes - Storage, insulation, shock absorb
Plasma cells - derived from lymphocytes
Leukocytes - derived from blood vessels, production of immunocompetent cells
Mast cells - surround blood vessels, contain granules of heparin and histamines
What are the main differences between loose and dense connective tissue?
Loose has higher ratio of cells and ground substance compared to fibres whereas dense has fewer cells and less ground substance and is more densely packed with fibres
What are the three types of fibre found in connective tissue?
3) Reticular (type III collagen)
Where is dense regular connective tissue found?
Tendons and ligaments
What is the purpose of dense irregular connective tissue in he dermis of the skin?
Can withstand and counteract the multidirectional forces applied to the tissue
Name 3 types of loose connective tissue
1) Mucous connective tissue (Wharton's jelly)
Of what embryonic origin is connective tissue derived from?
What is amorphous ground substance?
Gel-like matrix in which the fibres and cells are embedded in. The tissue fluids diffuse through. Composed of glycosaminoglycans, proteoglycans and glycoproteins
Where is mucous connective tissue ( Wharton's jelly) found?
Only found in the umbilical cord and subdermal connective tissue of the embryo
Where is areolar connective tissue found?
This is found:
- Deep under the skin
- In a layer beneath the epithelia of mucous membranes
- The submucosa
- Below the mesothelium of the peritoneum
- Associated with adventitia of blood vessels
- Surrounding the parenchyma of glands
What type of collagen is found in reticular fibres?
Where is dense irregular connective tissue found?
- Dermis of skin
- Deep fascia of muscles
- Dura mater
Describe dense irregular connective tissue
Interwoven bundles of collagen, which criss-cross each other in many directions.
This counteracts multi-directional forces to which the tissues are subjected.
The tissue is mostly collagen with small components of elastic and reticular fibres
Describe systemic sclerosis
All organs have excessive accumulation of collagen (fibrosis). This occurs in skin, digestive tract, muscles and kidneys - hardening and functional impairment
Describe scurvy (Vitamin C deficiency)
Defective collagen synthesis leading to degeneration of connective tissue. Periodontal ligament (with a high collagen turnover) is affected in scurvy, lessening of teeth in their sockets with subsequent loss (bleeding gums)
Describe Marfan's syndrome
Genetic defect (autosomal dominant) in chromosomes that code for fibrillin, which affects elastic fibres (undeveloped). Large elastic arteries (Eg aorta) rupture because of high blood pressure
Describe Ehlers Danlos disease
Deficiency in collagen type III (reticular fibres) causing ruptures in tissues containing high reticulin content
What cells secrete cartilage matrix?
What is an entrapped chondroblasts termed?
What type of collagen makes up hyaline cartilage?
What type of collagen makes up elastic cartilage?
What type of collagen makes up fibrocartilage?
Where is hyaline cartilage located?
- Respiratory passageway
- Articulate surfaces (ends) of long bones
- Anterior ends of the ribs Flexible and smooth to allow movement of tissues
Where is elastic cartilage found?
- Auditory tubes
- External ear
- Epiglotis Provides support and maintains the shape of structures
Where is fibrocartilage found?
- Intervertebral disc
- Pubic symphysis
- Portions of the tendons Support and rigidity as it is the strongest cartilage
What is the clinical relevance of hyaline cartilage, particularly with age?
- Can calcify/ossify in old age and disease
- Increased size/number of chondrocytes with age
Outline the characteristics of bone
- It can withstand compression, stress and deformation
- It's dynamic, responding to stress and strains by growth
- Bone is supplied with blood and lymph vessels as well as nerves making it sensitive to pain, especially the periosteum
- It contains cells, fibres and ground substance
Outline the functions of bone
- Support, protection
- Mineral storage
- Vascular connective tissue
- Appears as a compact (dense) form or sponge-like (cancellous) form. Cancellous is always surrounded by compact bone
Outline dense bone structure
- Concentric lamellae with central neuromuscular, Haversian canals, which communicate via Volkmann's canals
- Osteon - system of interconnecting canals present in compact bone
Outline spongy, cancellous bone
Meshwork of trabeculae filled with bone marrow
What stimulates osteoclast activity?
What inhibits osteoclast activity?
What are the three key cells found in bone and their functions?
1) Osteoblast - synthesise the organic components of cells, making bone. They produce the osteoid matrix
2) Osteocytes - found in the lacunae cavities, maintaining bone. They're formed when osteoblasts are entombed to produce osteocytes
3) Osteoclasts - large multinucleate cells from monocytes that digest bone
By what process does cartilage become bone and outline the process
- Cartilage reabsorbed and replaced with bone
- Begins at the primary centre in the shaft, the diaphysis
- This later begins form the secondary centre also, the epiphysis
- Growth in length occurs at the epiphyseal growth plate
By what process does loose connective tissue/Mesenchyme become bone and outline the process
- The bone begins as highly vascularised loose connective tissue
- Mesenchymal cells differentiate to osteoblasts which becomes the ossification centre
- They secrete uncalcified matrix (osteoid) and then become osteocytes
- Woven bone and periosteum form; Accumulating osteoid is laid down between embryonic blood vessels. The result is a network of lamellae
- Bone collor of compact bone forms and red marrow appears
Outline (basic) the cellular processes involved with bone repair
3) Cartilage callus
4) Primary bone
5) Secondary bone
Outline (detailed) the cellular processes involved with bone repair
1) Bone breaks
2) Bone matrix is destroyed and the bone cells adjoining the fracture will die
3) Inflammatory cells invade and form a pre-callus, which contains a blood clot (haemotoma) and fibrous tissue (If the periosteum is still intact a pro-callus is formed when the area is invaded by osteoclasts and macrophages which are more fibrous
4) An osteocallus of primary bone is made which is then calcified to secondary
5) The bone is pulled and pressured to match the contours of the surrounding bone (mainly via tendons) and eventually forms mature bone
6) Bone heals without forming scars
What is the end of a long bone called?
Whats is the long part of the bone called?
What is the cone shaped region that changes shape as we grow?
What are the parts of a flat bone?
Plates (inner and outer) and diploe (center)
What do osteoblasts differentiate into?
What is the organic portion of the matrix called?
What are needed for calcification for matrix?
Matrix vesicles (alkaline phosphatase and other enzymes)
What are spaces containing cell bodies?
What are spaces containing cytoplasmic processes?
What are the functions of osteoclasts?
Enzyme secretion, proton pumps to form an acidic environment, and degrade bone matrix
Functions of osteoclasts and osteoblasts are linked during what process?
Organic glycoprotein that is multi adhesive?
Organic glycoprotein that is calcium binding?
What are the main inorganic constituents of the matrix?
Calcium and phosphorus
What are plates along collagen fibres and surrounded by a hydration shell (fluid bound to crystals)?
What type of bone is highly ordered, has layers, is mature/secondary, and replaces woven bone?
What type of bone is primary and immature, lacking layers?
What lines the outer layer of bone?
What part of the periosteum contains osteoprogenitor cells that can differentiate to osteoblasts and chondroblasts?
The inner osteogenic layer
What part of the periosteum contains dense connective tissue?
Outer fibrous layer
Where are nociceptors in bone?
Bone is derived from which embryonic layer?
What is the resting zone in long bone?
Zone of reserve cartilage
What zone of the long bone has expansion of cartilage and increases length?
Zone of cell proliferation
What is the long bone zone where cartilage is resorbed, cells accumulate glycogen, and there is some addition to overall length, and a thin septa of matrix remain?
Zone of hypertrophic cartilage
What is the long bone zone where remaining cartilage matrix is calcified, calcium and alkaline phosphate, and chondrocyte apoptosis?
Zone of cartilage calcification
What is the long bone zone where much of cartilage matrix and cells are removed, capillaries invade, osteoblasts deposit osteoid over calcified cartilage?
Zone of Ossification
Incomplete calcification of bone occurs in children where bone is easily deformed and there is a decreased rate of bone growth
Adult rickets. Incomplete calcification of newly formed bone, decalcification of older matrix, and decreased calcium per unit of bone matrix in adults.
What causes incomplete calcification of bone?
Insufficient dietary Calcium or vitamin D
What are the most common sites of fracture?
Neck of the femur, wrist ankle In bone disease - pubic rams, spine, ribs, femoral neck