Lecture 15 - Blood, Bone Marrow & Blood Vessels

Question 1

What are the 5 different types (classifications) of bone?

Answer 1

1) Long
2) Short
3) Flat
4) Irregular
5) Sesamoid

Question 2

Describe the shape, location and 2 main functions of long bones.

Answer 2

• Longer than they are wide
• Mostly located on the appendicular skeleton, e.g.: femur and small bones in fingers (phalanges)
• Support weight of body + facilitate movement

Question 3

Describe the shape, location (2 main examples) and function of small bones.

Answer 3

• As long as they are wide
• Found in wrist and ankle joints (scaphoid in wrist, calcaneus in ankles)
• Provide stability + some movement

Question 4

Describe the shape, location (examples) and 2 main functions of flat bones.

Answer 4

• Flattened with somewhat parallel edges
• Ribs + sternum in thoracic cage, occipital bone in skull, ileum in pelvis
• Protect internal organs + provide large areas of attachment for muscle

Question 5

Describe the shape, give examples and explain the main function of irregular bones.

Answer 5

• They vary in shape and structure and are irregular as they dont fit into any other category
• Vertebrae & Sacrum
• Provides protection to organs, e.g.: vertebrae protects spinal cord + sacrum protects pelvic cavity organs.
• Also provides anchor points to muscle groups.

Question 6

Describe the location, give examples and provide the main function for sesamoid bones?

Answer 6

• Found embedded in the tendons of the hands, knees & feet, e.g.: the patella (generated post-natally)
• Provide protection to the tendons against repeated stress/wear and tear.

Question 7

Explain the structure of the 2 different areas formed in bone?

Answer 7

1) Cancellous bone - spongy network of fine columns to combine strength with lightness. Spaces filled with bone marrow
2) Compact bone - forms the external surfaces and comprises ~80% of bones skeletal mass.

Question 8

What are the 2 main types of bone marrow, their components and their functions?.
What is the special function of one of them?

Answer 8

1) Red Marrow - full of developing blood cells, only found in spongy/cancellous bone. Function = replenish blood cells (haemopoiesis).
2) Yellow marrow - full of adipocytes. Function = shock absorber and energy source.

Special function = yellow marrow can convert to red during anaemia.

Question 9

What repeating structures exist within cancellous bone and what cells are embedded within them?

Answer 9

• Trabeculae

- Osteocytes

Question 10

What are the 6 main cells that exist within the blood?

Answer 10

RBC’s, neutrophils, basophils, eosinophils, lymphocytes and platelets.

Question 11

What are the 2 main ways in which maturing cells leave bone?

Answer 11

1) Through sinusoids - which are 30-40um in diameter.

2) Large cells fit into sinusoidal space and fragment, e.g.: megakaryocytes fragment this way to form platelets.

Question 12

Describe the route of circulatory blood around the body.
How long do RBC’s take to mature?
Where do T + B cells mature?

Answer 12

• From the heart into arteries, arterioles then capillary beds. From here to venues, intermediate veins and veins into the vena cavae.
• 2 days
• T cells in thymus gland and lymphatic organs, B cells already mature

Question 13

What controls the flow of blood through capillaries?
Where is this located?
What does it contain to allow this?

Answer 13

• Pre-capillary sphincter
• In between the arterioles and capillary beds
• Smooth muscle for contraction

Question 14

What are veins?
Why do they require valves?
What are the 3 layers of veins and what do they contain?
What are the smallest and largest veins?

Answer 14

• Veins are elastic blood vessels that transport blood back to the heart.
• Veins are a low pressure system so require blood for unidirectional transport of blood.
  1) Tunica intima - endothelium layer (squamous epithelial)
  2) Tunica media - smooth muscle and elastic fibres
  3) Tunica externa/adventitia - elastic fibrous capsule
• Smallest = venules. Largest = vena cavae

Question 15

What are the 4 main types of veins and what do they do?

Answer 15

1) Pulmonary - carry oxygenated blood to left atrium from lungs
2) Systemic - carry non-oxygenated blood from body to right atrium
3) Superficial - close to skin surface and assist in homeostasis
4) Deep - surrounded by the viscera and organs of the body.

Question 16

What are the main differences between veins and arteries

Answer 16

• Veins carry blood back to heart, arteries away.
• Arteries have thicker walls (tunica externa) due to high BP
• Tunica media thicker in arteries
• Far less elastic tissue and muscle in veins
• Wide lumen in veins, narrow in arteries

Question 17

What are collateral vessles and when are they generated?

Answer 17

• Usually arterioles that provide protection to tissues that are compromised (e.g.: atherosclerotic plaque) by providing an alternative pathway for arterial blood.
• Generated due to chronic disease such as ischaemia or during development in the brain and joints.

Question 18

What are the 2 ways in which new blood vessels are produced? give an example of each.

Answer 18

1) Vasculogenesis - using angioblast precursors which split into primitive blood cells and endothelial cells to form a blood vessel - e.g.: during embryo development
2) Angiogenesis - formation of new blood cells from existing ones, e.g.: during foetal development or collateral arteries.

Question 19

Where are pericytes found + what do the do?

Answer 19

Pericytes sit on top of capillaries with lots of cytoplasmic extensions. They have contractile properties and are important in maintaining tight capillaries, e.g.: in BBB or in the retina. They also prevent endothelial cell proliferation.