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) (also part of appendicular skeleton)
• 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/Spongy bone - spongy network of fine columns to combine strength with lightness. Spaces filled with bone marrow
2) Compact/Cortical 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?
Which cells are on their surface which remodel the trabeculae?

Answer 9

• Trabeculae
• numerous osteocytes
• Osteoclasts and Osteoblasts

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 newly formed RBC’s around the body.
How long do RBC’s take to mature?
Where do T + B cells mature?

Answer 12

• Venule into intermediate vein, into larger vein then the vena cavae. From the vena cavae into the right atrium, out the aorta to pulmonary circulation, pulmonary artery then vein after lungs into left atrium, left ventricle and into artery for systemic circulation.
• 2 days
• T cells in thymus gland and lymphatic organs, B cells already mature

Question 13

What controls the flow of blood through capillaries and what is the function of this?
Where is this located?
What does it contain to allow this?
What happens to larger cells?

Answer 13

• Pre-capillary sphincter, control rate of fluid exchange between capillaries and tissue.
• In between the arterioles and capillary beds
• Smooth muscle for contraction - when closed blood cannot flow, when open blood can flow freely.
• Larger cells cannot pass through capillaries and bypass the capillary bed.

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 valves 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.
• Veins contain valves
• Arteries have thicker walls (tunica externa) due to high BP
• Tunica media thicker in arteries and has 2 distinct layers
• 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.