Histology

Question 1

Histologically, what do giant cell tumours consist of?

Answer 1

Multi-nucleate giant cells.

Question 2

Histologically what do giant cell tumours of the tendon sheath look like?

Answer 2

Multinucleated giant cells and haemosiderin.

Question 3

Macroscopically what do giant cell tumours of the tendon sheath look like?

Answer 3

Pigmented lesion.

Question 4

What doe skeletal muscle look like histologically?

Answer 4

Striated.

Unbranched.

Multinucleate (forms a syncytium).

Long cylindrical fibres.

Nuclei at the periphery of the fibre, just under the cell membrane (sarcolemma).

Question 5

What is a fascicle?

Answer 5

Muscle fibre are grouped into bundles called fascicles.

Question 6

What is the epimysium?

Answer 6

The connective tissue that surrounds the muscle as a whole.

Question 7

What is a perimysium?

Answer 7

The connective tissue that surrounds a single fascicle.

Question 8

What is an endomysium?

Answer 8

The connective tissue around a single muscle fibre.

Question 9

What is a sarcomere?

Answer 9

Unit of contraction of the muscle cell.

Question 10

What is a myofibril?

Answer 10

Thousands of sarcomeres placed end-to-end to form a myofibril.

Question 11

What does a motor unit consist of?

Answer 11

One motor neuron and all the muscle fibres it innervates.

Question 12

What is type I skeletal muscle?

Answer 12

Slow contracting fibres.

Oxidative metabolism.

Many mitochondria and myoglobin.

Resistant to fatigue.

Produce relatively less force.

‘Red’ fibres.

Question 13

What is type IIa skeletal muscle?

Answer 13

Intermediate speed in contracting.

Reasonably resistant to fatigue.

Relatively uncommon fibres.

Question 14

What is type IIb skeletal muscle?

Answer 14

Fast contracting fibres.

Anaerobic metabolism.

Few mitochondria and less myoglobin than type I.

Fatigue relatively easily and produce relatively greater force.

‘White’ fibres.

Question 15

What is cartilage?

Answer 15

Semi-rigid and deformable.

Permeable.

Avascular.

Cells nourished by diffusion through the extracellular matrix.

Question 16

What is bone?

Answer 16

Rigid.

Not permeable.

Cells within the bone must be nourished by blood vessels that pervade the tissue?

Question 17

What are chondrocytes?

Answer 17

Cells found in cartilage that live within a space in the EC matrix called a lacuna. Secrete and maintain the extracellular matrix surrounding them.

Chondroblasts are immature chondrocytes.

Question 18

What is type 2 collagen?

Answer 18

Fine and forms a 3D meshwork.

Question 19

What is type 1 collagen?

Answer 19

Thicker than type I and aggregates into linear bundles.

Question 20

What is hyaline cartilage?

Answer 20

Blue-white in colour, translucent and most common form of cartilage.

Question 21

What is elastic cartilage?

Answer 21

Light yellow in colour and flexible due to elastic fibres.

Question 22

What is fibrocartilage?

Answer 22

Hybrid between tendon and hyaline cartilage.

Densely packed bands of type I collagen interleaved with rows of chondrocytes, surrounded by small amounts of cartilaginous ECM.

Appears white.

Question 23

Where can you find hyaline cartilage?

Answer 23

Articular surfaces.

Tracheal rings.

Costal cartilage.

Epiphyseal growth plates.

Precursor in foetus to many bones.

Question 24

What is the function of bone?

Answer 24

Support.

Levers for effective movement.

Protection of internal organs.

Calcium store (>95% of total calcium in body is in the bone).

Haemopoiesis (blood cell production).

Question 25

What is bone composed of?

Answer 25

65% bioapatite (a form of calcium phosphate - mostly hydroxyapatite). 23% collagen. 10% water. 2%non-collagen proteins.

Question 26

What are the 2 types of bone?

Answer 26

Cortical bone. Cancellous or trabecular bone.

Question 27

What is cortical bone?

Answer 27

An outer shell of dense bone that makes up the shaft (diaphysis).

Question 28

What is cancellous or trabecular bone?

Answer 28

Found at the ends of the bone (epiphyses). Fine meshwork of bone.

Question 29

What is the difference between compact and trabecular bone?

Answer 29

Bone cells and matrix are similar in compact and trabecular bone. Both types are lamellar. Marrow cavities (spaces) are found adjacent to trabecular bone.

Question 30

What is an osteon?

Answer 30

Functional unit of compact bone.

Question 31

What are osteocytes?

Answer 31

A bone cell trapped within bone.

Question 32

What are osteoprogenitor cells?

Answer 32

Located on bone surfaces, e.g. under the periosteum, these cells serve as a pool of reserve osteoblasts.

Question 33

What are osteoblasts?

Answer 33

Bone forming cells found on the surface of developing bone. Have plentiful rough endoplasmic reticulum and prominent mitochondria.

Question 34

What are osteoclasts?

Answer 34

Large multinucleated cells found on the surface of bone and are responsible for bone resorption.

Question 35

What is bone remodelling?

Answer 35

Osteoclasts congregate and begin to 'drill' into the bone forming a tunnel. A blood vessel grows into the tunnel bringing with it osteoblasts which line the tunnel and begin laying down new lamellar bone. Process continues until only the space of a Haversian canal remains.

Question 36

What is a basic multicellular unit?

Answer 36

The collection of osteoclasts and osteoblasts that participate in bone remodelling.

Question 37

What is a Haversian canal?

Answer 37

Small canals which form a network in bone and contain blood vessels.

Question 38

What is osteoid?

Answer 38

The osteoblasts that secrete collagen along with glycosaminoglycans, proteoglycans and other organic components of the bone matrix.

Question 39

What is bone mineralisation?

Answer 39

Osteoid is the progenitor material that becomes hardened as it attracts calcium phosphate. ## Footnote *Thus osteoblasts don't secrete bone directly by indirectly.*