Lecture 13- Bone, Bone Marrow , Vessels And Blood Flashcards
State the 5 types of bones
Long
Short
Flat
Irregular
Sesamoid (sesame seed-like)
Structure of long bones
- longer than they are wide
- includes femur (longest bone in the body ) and small bones in the finger
Where are long bones located ?
Mostly located in the appendicular Skeleton
Function of long bones
To support the weight of the body and facilitate movement
Structure of short bones
Approximately as long as they are wide
Location of short bones
- wrist and ankle joints
- the carpals in the wrist (scaphoid) and the tarsals in the ankles (calcaneus)
Function of short bones
Short bones provides stability and some movement
Structure of flat bones
Somewhat flattened with roughly parallel opposite edge
Curved
Location of flat bones in the body
- in the skull (occipital)
- thoracic cage (sternum and ribs)
- pelvis(ilium)
Functions of flat bones in the body
- protects internal organs
- also provides large areas of attachments for muscles
Structure of irregular bones
- vary in shape and structure
- often have a fairly complex shape
E.g vertebrae
Function of irregular bones in the body
- protects internal organs
- vertebrae in the vertebrae column protects the spinal cord.
- pelvis(sacrum) protects organs in the pelvic cavity
- provides important ‘anchor’ points muscle groups
Structure of sesamoid bones
-small round bones that are found in the tendons of hands, knees and feet
E.g Patella -generated postnatally
Functions of sesamoid bones
- protects tendons from stress and damage from repeated ‘wear and tear‘
A bones is made up of 2 different structures of bones. What are they ?
Cancellous bone
Compact bone
Features of a cancellous bone
Spongy
Spaces (medullary region ) are filled by red and yellow bone marrow
Features of compact bone
- forms the external surfaces (around the edges)
- thin at the head and gets thick towards the middle
Key features of red bone marrow
- full of developing blood cells
- rich blood supply so its very red
- only found in spongy Bone
Function of the red bone marrow ?
To replenish cells of the blood (haemopoiesis)
Key features of yellow bone marrow?
- full of adipocytes
- poor blood supply => yellow
- can differentiate into red blood cells, fibroblasts and myocytes
Function of yellow bone marrow ?
Shock absorber and energy source
Can convert to red marrow
What is meant by the term trabeculum (singular)?
Structures that surrounds the spaces containing bone marrow and blood vessels
How do maturing cells leave the bone ?
They leave through the veins after being collected from the bone marrow due to the sinusoid always capillaries .
How are platelets released ?
Platelets are released from a megakaryocyte via apocrine
On entering circulation , how does RBCs travel?
They travel from
Venule -> intermediate vein -> larger vein ->vena cava
*newly formed WBCs take same route
How long does it take red blood cells to become mature?
2 days
What is the flow in the capillaries controlled by ?
Precapillary sphincters
Where are the precapillary sphincters located and how do they work ?
Located between arterioles (smallest arteries ) and capillaries
- contain smooth muscles so contraction occurs
- when opened, blood flows freely to the capillary beds
- when closed, blood is not allowed to flow through capillary beds
Function of precapillary sphincters in the capillaries
Controls fluid exchange between the capillaries and the body tissues that takes place at the capillary bed
State the 3 layers on the vein
- Tunica intima - endothelial cells
- Tunica media - elastic fibres and smooth muscle cells
- Tunica externa - elastic fibrous capsule
How does the blood get to the heart at low pressure system ?
Relies on muscle contractions and valve to return blood to the heart
E.g calf muscles compress to aid movement against gravity
State the 4 main types of Veins ?
- pulmonary veins
- systemic veins
- superficial veins
- Deep veins
Role of pulmonary veins
Carry oxygenated blood from lungs to left atrium of the heart
Role of systemic veins (Superior and inferior vena cava)
Return oxygen depleted blood from the rest of the body to the right atrium of the heart
Role of valves in veins
Non return valves work against gravity to prevent backflow
Location of superficial veins
Located close to the surface of the skin and re not located near a corresponding artery
Location of deep veins
Located deep between tissues and are typically located near a corresponding artery with the same name
E.g Renal vein and renal artery
3 main layers of arteries
Tunica intima - non fenestrated , elastic membrane lining and smooth endothelium
Tunica media - smooth muscle and elastic fibres
(Thicker in arteries than veins and has two distinct elastic layers )
Tunica externa - the strong outer covering composed of collagen and elastic fibres
*small lumen
Arteries
Structure relating to function
- strength and elasticity needed to withstand pulsing of blood, prevent bursting and maintain pressure wave
- helps maintain high blood pressure by preventing blood flowing backwards
Capillaries
Structure relating to function
- no need for strong walls and most of pressure has been lost
- thin walls and narrow lumen bring blood into close contact with body tissue thus allowing diffusion of materials between capillaries and surrounding tissue .
- while blood cell can squeeze between cels of walls cause they are fenestrated
Veins
Structure relating to function
- no need for strong walls, as most of the blood pressure has been lost
- wide lumen offers less resistance to blood flow
Key features of collateral blood vessels
- provide protection for tissues that may become compromised
- provides alternate path for arterial blood flow
- some generated due to reduced blood flow (ischaemia)
- some produced during development
Takes tome to develop
What is Vasculogenesis ?
Examples?
Formation of new blood vessels from angioplast precursors (bone marrows)
During embryo development (heart and primitive vascular plexus), newly formed cancers, endometriosis
What is angiogenesis ?
Example?
Formation of new blood vessels from existing blood vessels
During feral development , collateral arteries , postnatal lung development
Structure of the pericyte?
- immature smooth muscle like cell
- found inside basal Latina, close to basal membrane
- key components of capillaries
- have contractile properties
- involved in nerve cell communication
What are pericytes able to differentiate into?
Endothelial cell
Smooth muscle cell
Fibroblasts
Functions of pericytes ?
Prevents endothelial cell proliferation
Maintains tight capillaries e.g blood brain barrier , in the retina etc
