Essentials Of Clinical Medicine 7

Front 1

What 3 things do all connective tissues consist of?

Back 1

Cells, fibres and matrix

Front 2

How can connective tissues be classes?

Back 2

Either proper connective tissues, or special connective tissues

Front 3

What are the 3 resident cells of proper connective tissues and what are their roles?

Back 3

1. Fibroblasts = synthesis of fibres and ECM. Have fat rounded nuclei (fibrocytes have thin, long nuclei)
2. Adipocytes = storage cells appearing like signet rings. Can also act as a shock absorber and insulator
3. Defence cells = macrophages and mast cells. Macrophages make antibodies and recruit cells to infection, in addition to phagocytosing foreign material. Mast cells release locally active substances e.g. histimine

Front 4

Describe the fibre types in connective tissue and the functions of each

Back 4

1. Collagen
- Found in all connective tissues
- Many forms = Types I to IV most important. Type I = in bone, skin and tendon. Type II = In some types of cartilage. Type III = reticular fibres supporting cells in some organs. Type IV = found in the basal lamina of epithelial cells

2. Elastic fibres
- Formed of elastin and microfibrils
- Allow tissues to respond to stretch and strain
- Found in the walls of some blood vessels, the skin, etc

Front 5

How can proper connective tissues be classified and describe the features of each type?

Back 5

Loose connective tissue: Few fibres, cells/matrix predominate. Tends to be found as packing material in many organs and is characteristially present below the epithelial layer

Dense connective tissue
- Regular = mainly fibres in a regular arrangement
- Irregular = mainly fibres in a irregular arrangement e.g. in the dermis of skin helps to anchor the surface skin to underlying layers

Front 6

What is cartilage (4)?

Back 6

- Special connective tissue
- Forms the framework of various structures e.g. the external ear and epiglottis
- Predominately matrix (fibres and particularly ground substance)
- Comes in 3 forms: hyaline, elastic and fibrocartilage

Front 7

Describe the features of hyaline cartilage

Back 7

- Made up of type II collagen
- Commonest form of cartilage
- Found in the trachea and the surfaces of joints (where missing perichondrium and known as articular cartilage)

Front 8

Describe the features of elastic cartilage

Back 8

- Similar to hyaline cartilage but major component is elastic fibres and only a small amount of Type II collagen
- Often makes up skeleton of structures requiring flexibility e.g. pinna of ear and epiglottis

Front 9

Describe the features of fibrocartilage

Back 9

- Contains thick bundles of Type I collagen fibres and relatively scattered cartilage cells
- Very strong and resistant to stretching = found in IVDs and pubic symphysis

Front 10

Describe the histology of smooth, skeletal and cardiac muscle

Back 10

- Smooth muscle = central nuclei with no striation
- Skeletal muscle = lateral nuclei with striation
- Cardiac muscle = central nuclei with striation and branching fibres

Front 11

Describe the ultrastructure of the skeletal muscle and how it relates to its function

Back 11

1. Skeletal muscle is surrounded by a loose connective tissue sheath called the epimysium
2. Groups of muscle fibres (cells) are packaged together to form a fascicle wrapped in perimysium
3. Each muscle cell is surrounded by the sarcolemma (cell membrane) and contains numerous myofibrils
4. Myofibrils contain lighter I bands (actin) and darker, thicker A bands (myosin) where the M line is the centre of the A band (in the H zone) and contains no actin, and the Z disc is at the centre of interdigitating actin bands and contains no myosin. A sarcomere is Z-disc to Z-disc
5. Each fibril is surrounded by tubules. T-tubules make contact with the sarcolemma transversely, holding fibrils together. Reticulum fibres run longitudinally along the cell and have swollen ends which abut onto T-tubules forming terminal cisternae of the sarcoplasmic reticulum
6. In movement the action potential is propergated down the sarcolemma and triggers calcium release from the terminal cristae of the SR. This causes the actin to move along the myosin, so that the H-bands and Z-bands get smaller, and the A-bands stay the same

Front 12

Describe the ultrastructure of the cardiac muscle and how it relates to its function

Back 12

- Similar structure to skeletal muscle sarcomere, with alternating A and I bands and Z lines.
- Individual cells are very small and are connected by intercalated discs
- Intercalated discs have 2 functions = mechanically joins 2 adjacent cells & gap junctions put 2 muscle cells into electrical continuity = synchronous contraction