Bone, Bone Marrow, Vessels and Blood

Question 1

What are the 5 main types of bone found in the body? Give an example of each.

Answer 1

Long - femur
Short - carpals and tarsals
Flat - sternum, skull, ribs
Irregular - vertebrae
Sesamoid - patella

Question 2

If we slice a femur along the sagittal plane and inspect it we can find two types of bone in the femur. Which?

Answer 2

Cancellous bone

Compact bone

Question 3

What is the main difference between cancellous bone and compact bone?

Answer 3

Compact bone is much denser than cancellous bone. 80% of the body’s skeletal mass consist of compact bone, that doesn’t mean volume wise that there is more compact bone however.
Cancellous bone is more porous where in between the spaces bone marrow is filled with.

Question 4

There are two types of bone marrow. Which?

Answer 4

Red marrow

Yellow marrow

Question 5

How does red marrow and yellow marrow differ?

Answer 5

Red marrow is full of developing cells and rich in blood supply. Its function is to replenish cells in the blood (haemopoeisis)
Yellow marrow is full of adipocytes and has a poor blood supply. Its function is to work as a shock absorber and energy source.

Question 6

Where can you find red marrow?

Answer 6

Only in cancellous bone

Question 7

Where can you find yellow marrow?

Answer 7

In both cancellous and compact bone

Question 8

How does the composition of marrow differ from a new born to a 50 year old man?

Answer 8

As you age red marrow will gradually turn into yellow marrow. This means that a 50 year old man will have more yellow marrow and therefore more adipocytes.

Question 9

We established that red marrow can turn into yellow marrow. Is the reverse possible?

Answer 9

Yes in case of immense blood loss or other reason yellow marrow can turn into red marrow to support blood supply.

Question 10

What are the 7 main cells found in blood?

Answer 10

RBCs, Basophils, Eosinophils, Neutrophils, Lymphocytes, Monocytes and Platelets.

Question 11

How do maturing cells leave the bone and the bone marrow?

Answer 11

The bone marrow is full of sinusoids. Mature cells can squeeze through the sinusoids of the vessels. This is with the help of glycophorins and aquaporins.

Question 12

As red blood cells are released from the bone marrow, where do they enter the circulation of the blood system?

Answer 12

They enter a venule -> intermediate vein -> larger vein -> vena cava.

Question 13

Where does RBC become mature?

Answer 13

In circulation and during it.

Question 14

How long does it take for a RBC to become mature?

Answer 14

2 days.

Question 15

As white blood cells are released from the bone marrow, where do they enter the circulation of the blood system?

Answer 15

The same as RBCs. Venule -> intermediate vein -> larger vein -> vena cava.

Question 16

How do WBCs become mature?

Answer 16

By activation. T cells need the actions of the thymus and lymphatics.
B cells are already activated.

Question 17

What is the flow in capillaries controlled by? (What makes them either contract or dilate)

Answer 17

Precapillary sphincters

Question 18

What is a circulatory anastomosis?

Answer 18

A connection between either two veins, two arteries or and artery and vein. They provide a different path to blood flow in case the main route is blocked or compromised. Sometimes they occur naturally in the body but sometimes it is an indication of a pathological abnormality.

Question 19

What is the function of capillaries?

Answer 19

To allow exchange of material to nearby tissue. Capillaries are only one cell layer thick (simple squamous).

Question 20

Define veins:

Answer 20

An elastic blood vessel that carries blood from various region back to the heart.

Question 21

How many layers do veins consist of? Name them. Also mention what is found in each layers

Answer 21

3 layers
Tunica Intima (endo/epithelial cells)
Tunica Media (Elastic fibres and smooth muscle cells)
Tunica Adventitia (elastic fibrous capsules / collagen / elastic fibres)

Question 22

Since veins are a low pressure system and sometimes work against gravity, how is blood carried back to the heart?

Answer 22

Relies on muscle contraction, like walking and running.

Contraction and compression aids the blood flow in veins.

Question 23

How come there is no back flow of blood in veins?

Answer 23

Because veins have fibroelastic cartilaginous valves that prevents back flow.

Question 24

What are the 4 main types of veins?

Answer 24

Pulmonary veins (oxygen rich)
Systemic veins (oxygen poor)
Superficial veins (close to skin)
Deep veins (deep in body)

Question 25

What is the smallest vein called?

Answer 25

A venule

Question 26

What is the largest vein called?

Answer 26

Vena cava

Question 27

Define arteries:

Answer 27

Elastic blood vessels that carry blood away from the heart.

Question 28

How many layers do arteries consist of? Name them. Also mention what is found in each.

Answer 28

Tunica Intima - endothelial/epi cells with an elastic membrane
Tunica Media - smooth muscle cells and elastic fibres
Tunica Adventitia - collagen and elastic fibres

Question 29

How do veins and arteries differ structurally?

Answer 29

Veins have a larger lumen than arteries. The lumen is also usually circular in arteries where this is not usually the case in veins.
Arteries have a thicker tunica media with distinct elastic membranes surrounding each side of the tunica media. This is to withstand more pressure.
Arteries do not have any valves.
Arteries also have an internal elastic membrane in the tunica intima.

Question 30

Why are the walls of arteries thicker than veins?

Answer 30

To deal with higher blood pressure.

Question 31

What is vasculogenesis? When does this happen?

Answer 31

Formation of new blood vessels from ‘nothing’ (angioblast precursors from bone marrow)
During embryonic development.

Question 32

What is angiogenesis? When does this happen?

Answer 32

Formation of new blood vessels from existing blood vessels.

During fetal development. Also in the formation of collateral arteries.

Question 33

What is the function of the pericyte?

Answer 33

Prevent proliferation of endothelial cells

Maintain light capillaries.