Session 8 ILOs - Bone, bone barrow and haemopoiesis

Question 1

Describe the characteristic features and functions of the different types of bone in the body

Answer 1

Long:
- Longer than they are wide
- Mostly in the appendicular skeleton
Function: Support and movement 
Example - Femur

Short:
- Wider than they are long
- Mostly in the wrist and ankle joints
Function: Stability and movement 
Example - Wrist bones

Flat:
- Flattened and roughly parallel at the edges
Function: Protection and large surface area for attachment
Example - Skull or pelvis

Irregular:
- Vary in shape 
- Tend to have a specialised shape for their function (complex)
Function: Protection and anchor points
Example - Vertebrae

Sesamoid (pea-like):
- Bones embedded in tendons
- Small, round bones
Function: Protect tendons from stress and damaged
Example - Patella (also in hands and feet)

Question 2

Describe the constituents of bone marrow and how they differ from cells in blood in structure and function

Answer 2

Constituents of bone marrow - 2 types:

1. Red bone marrow
   - Found in spongey bone
   - Contains developing RBCs
   - Rich blood supply
   Function: replenish cells in the blood
2. Yellow bone marrow
   - Found at the centre of bones
   - Full of adipocytes
   - Poor blood supply (doesn’t need it)
   Function: shock absorber and energy supply

Question 3

Describe the structure of blood vessels of the arteries and veins (plus capillaries)

Answer 3

Arteries:
Tunica intima - elastic fibres and endothelium (not fenestrated)
Tunica media - elastic fibres and smooth muscle
Tunica externa/adventia - elastic fibres and collagen

Veins:
Tunica intima - endothelial cells
Tunica media - elastic fibres and smooth muscle
Tunica externa/adventia - elastic fibrous capsule (lots of collagen)

Capillaries:
- Endothelium surrounded by basement membrane

Question 4

Explain how blood vessels are generated

Answer 4

By either of the following 2 ways:

1. Vasculogenesis
   - Mesenchymal stem cells come together and produce growth factors
   - Change the phenotype and forms an angiogenic cluster
   - Cells split to form a blood vessel
2. Angiogenesis
   - Stimulus causes the cells to release FGF or VEGF
   - Endothelial cells grow away from the stimulus

Question 5

Describe the differences between plasma and serum

Answer 5

Plasma is the liquid portion of anti-coagulated blood (has clotting factors in it) and serum is the liquid portion of coagulated blood (has no clotting factors)

Plasma:

• Plasma (has clotting factors)
• Buffy coat (WBCs and platelets)
• RBCs

Serum:

• Serum (no clotting factors)
• Blood clot

Question 6

The importance of platelets (thrombocytes) - A clinical example

Answer 6

Platelets are important in stopping bleeding - contain vast amounts of proteins and clotting factors
Have special receptors on the surface that because platelet aggregation

EXAMPLE: Thrombocytopenia

• Easy or excessive bruising (purpura)
• Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae)
• Prolonged bleeding from cuts
• Although rare, severe thrombocytopenia can cause bleeding into the brain, which can be fata.

Question 7

Describe Erythrocytes and reticulocytes and their functions

Answer 7

Eryhtrocytes (RBCs):
- Biconvex shape
- No nucleus (minimal organelles)
- No mitochondria
Function: To carry oxygen around the body via haemoglobin

Reticulocytes (immature RBCs):
- Small amount of RNA present to help synthesise haemoglobin
- No nucleus
Function: High amounts when body is recovering from blood loss - precursor to RBCs

Question 8

Describe Granulocytes or polymorphonuclear leucocytes (i.e. neutrophils, basophils, eosinophils, monocytes) and their functions

Answer 8

Neutrophils:
- Largest (excluding macrophages)
- Multilobe nucleus
- Lots of granules (3 diff. types)
Function: first line of defence, can kill bacteria in multiple ways e.g. NETS or phagocytosis

Basophils:
- Bilobed nucleus
- Stains basic dyes (blue/purple granules)
- Granules which contain histamine and heparin (anti-clotting factor)
Function: trigger inflammation and hypersensitivity reactions

Eosinophils:

• 2 nucleus lobes
• Phagocytose pathogens
• Acid loving granules (pink)

Monocytes (differentiate into macrophages)

• First line of defence
• Very largest
• Best of phagocytosis
• Unilobe horse-shoe nucleus

Question 9

Describe Lymphocytes and their functions

Answer 9

B lymphocytes:
Function: Antibody producing cells
- Can activate T cells
- Humoral response

T lymphocytes:
Function: Kill virus infected cells, cancer cells or transplanted tissue
- Antigen presenting cells
- Cell mediated response
- Can activate B cells via IL4

Question 10

Describe platelets (thrombocytes) and their functions

Answer 10

Platelets are small, clear, irregularly-shaped cell fragments formed from megakaranocytes disintegrating
- Platelets have no nucleus

Functions:

• Blood clotting
• The adhesive surface proteins of platelets allow them to accumulate on the fibrin mesh at an injury site to form a platelet plug that clots the blood
• If the number of platelets is too low, excessive bleeding can occur and wound healing will be impaired. However, if the number of platelets is too high, blood clots can form (thrombosis).

Question 11

Describe platelets and their functions

Answer 11

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