Lecture 14: bone, BM, vessels & blood

Question 1

What are the 5 types of bone?

Answer 1

Long
Short 
Flat
Sesamoid
Irregular

Question 2

What is the function of long bones?

Answer 2

support body weight and facilitate movement

Question 3

What is the function of short bones?

Answer 3

Stabilise and provide movement

Question 4

Name 3 flat bones of the body and their general functions.

Answer 4

Cranial bones
Sternum 
Ribs
Pelvic
Scapulae

Protect internal organs
Large areas for muscle attachment

Question 5

Name some irregular bones of the body and their general functions.

Answer 5

Vertebrae
Sacrum

General internal organs
Vertebrae = spinal cord protection
Become anchor points for muscles

Question 6

Name a sesamoid bone of the body and their general functions.

Answer 6

Patella

Protect tendons from stress and damage from repeated wear & tear

Question 7

Describe the difference between cortical and cancellous bone.

Answer 7

Cortical forms the external part of bone and is majority of bone.
Compact is the internal part which is spongier and more spaces for BM to fill.

Question 8

What components of BM are there?

Answer 8

Red marrow: only in cancellous bone and erythropoiesis to replenish RBCs
Yellow marrow: full of adipocytes = shock absorber + energy store

Question 9

What can the BM do when there is a bleed?

Answer 9

Red marrow = erythropoiesis

Yellow marrow = converts –> red for more erythropoiesis

Question 10

What do we mean by trabecullae?

Answer 10

They are the small columns of bone that make up a space-filled network within the cancellous bone.

Question 11

Within spongy bone, where do we find the osteoblasts, osteocytes and osteoclasts?

Answer 11

The osteoblasts and osteoclasts are on the peripheral of the lamellae for remodelling. Osteocytes are embedded within the lamellae.

Question 12

How do maturing blood cells leave the bone?

Answer 12

Most haemocytes leave via sinusoids to the periosteum.
HSC-> developing megakaryocyte in extracellular matrix-> megakaryocyte attaches to blood vessel–> cytoplasmic projections apocrine secrete via fenestrations into bloodstream.

Question 13

How is a sinusoid different from a continuous and fenestrated vessel?

Answer 13

Sinusoid has an incomplete basement membrane to allow whole cells to squeeze through.

Question 14

When mature cells leave the bone, in what order of blood vessels does it travel through?

Answer 14

Venules, intermediate veins, larger veins, vena cava.

Question 15

What are precapillary sphincters and what is their connection to microcirculation?

Answer 15

SM that constrict capillary lumen and found between arterioles and capillaries. They control the fluid exchange between capillaries and somatic tissues.

Question 16

Metarterioles are structures found near capillaries. What is their role?

Answer 16

They create another pathway for larger blood cells to travel along which allows them to bypass the capillary bed.

Question 17

Describe the structure of a vein.

Answer 17

Tunica intima: endothelial cells that line the lumen
Tunica media: thin layer made of mostly elastic fibres and SM
Tunica externa: thick elastic fibrous capsule that maintains vessel’s shape.
Venous valve: fibroelastic cartilaginous valve that prevents backflow

Question 18

What are the 4 types of veins and which one’s function is slightly different?

Answer 18

pulmonary: carries O2 blood instead of deO2 blood like the other veins
systemic: returns deo2 blood to the RA
superficial: located close to surface of skin and not usually near corresponding arteries
deep: deep between tissues and near corresponding arteries.

Question 19

Describe the structure of an artery.

Answer 19

Tunica intima: elastic smooth endothelium
Tunica media: SM and elastic fibres for expansion and return to original shape
Tunica externa: strong, thicker outer layer of collagen and elastic fibres.

Question 20

What is the purpose of collateral blood vessels?

Answer 20

provide an alternative path for arterial blood flow when the tissue has been compromised.

Question 21

What is the difference between vasculogenesis and angiogenesis?

Answer 21

Vasculogenesis is the formation of blood vessels from angioblast precursors
Angiogenesis is blood vessel formation from existing blood vessels

Question 22

There are 2 forms of angiogenesis: sprouting and intussusception. How do these 2 develop differently after a single vessel has been produced?

Answer 22

After a single vessel is produced (with VEGF), the single vessel can take 2 paths.

Sprouting: FGF stimulate the process of pericytes to convert into SM cell. This takes a long time.

intussusception: Multiple GF are used to split the singular vessel into 2 (twinned vessels). This explains why arteries and veins are close together in neurovascular bundles. This takes less time.

Question 23

Pericytes are similar to SM cells. Where can they be found and relate their properties to their role?

Answer 23

They can be found in the basal lamina very small vessels. (Retina, BBB)
They prevent endothelial division and maintain tight capillaries: they can differentiate into endothelial, SM & fibroblast cells. As a result, they can prevent fluid leaks out of the small vessels.

Question 24

If a patient comes in and you find they have hypertension, how would this affect the layers of a large artery/vein?

Answer 24

Tunica externa will deposit more extracellular matrix.
Tunica media will get damaged so the SM will proliferate and via hyperplasia.
Tunica intima: damaged so could lead to atherosclerosis.

Question 25

A man has anaemia. His biopsy shows normal BM which suggests that cells are unable to leave the BM or are destroyed as soon as they leave. Which specific vascular structure would the RBCs have left the BM via?

Answer 25

Intercellular gaps in sinusoidal vessels as these have gaps large enough for erythrocytes to travel through/ change shape through.

Question 26

A girl has a misshaped head (craniosynostosis) where the occipital bone at the back of her head is asymmetrical. The bony plates of the skull fused prematurely due to overactive osteoprogenitor cells.

Where, in the developing girl’s fetal occipital bone, would these cells normally be found?

Answer 26

They would be found in centre of the developing bone. This allows them to differentiate into osteoblasts that line the periosteum and gradually differentiate into osteocytes during bone formation.

Question 27

A man has fracture a bone in their had. During recovery of bone repair process, he is advised to eat well so that all the bone-maintenance cells have all the nutrients and O2 they need to speed up the healing process.

Which component of bone tissue impedes the distribution of nutrients and O2 to his osteocytes?

Answer 27

Extracellular matrix as this mineralised substance is impervious to aqueous solutions. Hence, ionic nutrients and O2 would not pass through as easily.