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What are the four main tissue types in the body?
What do the following types of cells present in all types of connective tissue do? a) Fibroblasts b) Macrophages c) Adipocytes d) Mesenchymal cells e) Melanocytes f) Mast cells g) Lymphocytes h) Plasmocytes i) Neutrophils j) Eosinophils
- a) Most common, secrete hyaluronan and protein fibres
- b) defensive cells that phagocytose pathogens
- c) Store lipid droplets
- d) Stem cells, aid during infection or in repair of an injury, provide daughter cells that can differentiate to replace dead or injured cells
- e) Synthesise and store melanin
- f) Carry histamine to stimulate local inflammatory response
- g) Circling defenders, WBCs
- h) Produce and secrete antibodies
- i) First line of defence, phagocytic
- j) Can be phagocytic, help attack parasites
What type of fibres can be found in connective tissue?
- Collagen - long, straight, unbranched, made of collagen protein. Very touch and strong. Up to 15 different types.
- Reticular - made of collagen but thinner. Form an interwoven network that is flexible and resistant to forces (helps hold blood vessels in place)
- Elastic - made of elastin protein. Can be branched and wavy, will return to original shape.
What cells are found in adult cartilage? And what is their function?
- Chondroblasts - produce ECM
- Chrondrocytes - maintain ECM
True or false: cartilage has a blood supply?
False - it is maintained by simple diffusion of nutrients from blood vessels that pass close by
What are the three types of cartilage?
What is the most common type of cartilage?
Describe the development of the skeleton
The first skeletal organisation of the foetus is entirely cartilaginous. The cartilage is then replaced by bone. The foetus still has to be able to grow so not all areas of the body become completely ossified e.g. growth plates of long bones.
Give an example of where hyaline cartilage is located in adults
Articular joint surfaces, walls of respiratory passages (larynx and trachea), costal cartilages
Explain the difference between appositional and interstitial growth
- Appositional growth is the formation and deposition onto the surface of pre-existing cartilage. Chondroblasts come from the surrounding interstitial tissue. Also fibroblasts, if given the right signal, can differentiate into chondroblasts. They then start to make an ECM similar to what cartilage is made of. The cells move away from the periochondrium by surrounding themselves with ECM.
- Interstitial growth occurs within the cartilage model. The cartilage is able to undergo developmental processes within itself and create a swelling of cartilage from within. Chondrocytes form isogenous groups and deposit ECM.
What is an isogenous group?
Chondrocytes in clusters of four cells surrounded by their ECM
Give an example of an area of the body where hyaline cartilage only grows by interstitial growth
Articular cartilage. At joints cartilage is constantly worn away by bones grinding against each other so it has to be able to repair itself. On histological section there is no evidence of a perichondrium - only synovial fluid which nourishes the cartilage.
Give an example of an area of the body where elastic cartilage is found
Ear pinna, epiglottis
How does elastic cartilage grow?
Appositional and interstitial growth
What advantage is there in having a high elastic content in elastic cartilage?
Give an example of an area of the body where fibre-cartilage is found
- Intervertebral discs
- Intra-articular discs (menisci)
- Attachment of ligaments and tendons to bones
How are the chondrocytes arranged in fibro-cartilage?
They are arranged between bundles of collagen type 1
How does fibro-cartilage grow?
Interstitial growth only (no identifiable perichondrium)
What parts of a bone do the following terms correspond to: diaphysis, metaphysis, epiphysis?
- Diaphysis - shaft or body
- Metaphysis - junction between diaphysis and epiphysis
- Epiphysis - end of the bone
What type of connective tissue is present on the outer surface of all bones?
What are the two main types of bone?
Lamellar and woven
What are the two types of lamellar bone?
Compact/cortical and spongy/cancellous/trabecular
Where is compact bone found in a bone?
In the diaphysis
What is the basic unit of compact bone?
Osteone or Haversian system
Briefly describe the structures of an osteone
Central blood vessel and connective tissue, oestocytes within lacunae linked by canniculi arranged in bony layers
Describe the structure of spongy bone
Spicules are aggregated into bony trabeculae. Spaces between trabecule consist of CT (endosteum) and blood vessels.
Give examples of when woven bone is present in the body
Developing bone (first bone present in the developing embryo), fracture repair, bone tumours
List some functions of bone
- Rigid and hard support
- Protects vital organs
- Contains the bone marrow (haematopoiesis)
- Reservoir for calcium, phosphate and other ions
- Transforms forces of skeletal muscle contraction into bodily movements
What are the three main types of bone cells? And what are their function?
- Osteoblasts - synthesis of osteoid
- Osteocytes - maintain the bony matrix
- Osteoclasts - enzymatic digestion of bony matrix - remodelling
Where do osteoblasts originate from in bone?
Periosteum and endosteum
Where are osteocytes found in bone?
They are located in lacuna between lamellae of calcified osteoid
How do osteocytes communicate?
Where do osteoclasts originate from?
Where are osteoclasts found in bone?
Periosteum and endosteum
What do osteoclasts look like?
They are large, multinucleated cells with a characteristic ruffled border
What makes up the a) organic b) inorganic component of osteoid?
- a) Fibres - mostly collagen type 1, GAGS, Glycoproteins
- b) Hydroxyapatite crystals, Na, Mg, Fe