What components make up blood?
Plasma (55%)
Red cells (erythrocytes)
White cells (leukocytes)
Platelets
What is in the blood plasma?
Water (90%)
Proteins
Nutrients
Salts
What are erythrocytes?
Red blood cells
What are leukocytes?
Name 5
White blood cells
- neutrophils
- eosinophils
- basophils
- lymphocytes
- monocytes
What are platelets?
Cell fragments, 2 micrometers, involved in hemostasis
Well developed cytoskeleton which aids extrusion of granules and the clotting
Some organelles, no nucleus
Contain coagulation factors within some granules
What is the internal elastic membrane?
Layer of elastic tissue separating tunica intima and tunica media
What is the external elastic membrane?
Layer of elastic tissue separating tunica media from tunica adventitia
Do elastic fibres show up with common stains?
No, specialised stains must be used
What are elastic arteries?
Large arteries which contain less smooth muscle and more elastic fibres within tunica media to enable them to stretch and shrink during the cardiac cycle and maintain consistent blood pressure
What is the vaso vasorum?
Blood supply to tissues within large blood vessel wall (excluding tunica intima)
Why do tissues in the large blood vessel walls need a separate blood supply?
Only tunica intima can access nutrients and oxygen from blood in lumen
How is the vessel wall of a small arteriole different to that of an artery?
Less smooth muscle
Very small tunica adventitia
What are vaso nervorum?
Nerves supply blood vessels
Describe the structure of a capillary
No smooth muscle
Simple squamous epithelial cells connected to basal lamina
Diameter of 4 - 8 micrometers (RBC is 7 micrometers)
Name the three types of capillary
Continuous
Fenestrated - contain small pores
Discontinuous / sinusoidal - contain large gaps between cells
At what point does capillary turn into a venule?
When patches of smooth muscle start to appear in the tunica media
Where do capillaries drain to?
Post - capillary venules consisting of endothelial cells and thin layer of connective tissue
Important site for exchange eg cells from blood can move into tissues during inflamation response
Describe structure of veins
Contain valves to prevent backflow of blood
Thin tunica media with a layers of few smooth muscle cells
Substantial tunica adventitia
Largest veins have very large tunica adventitia with bundles of longitudinal smooth muscle
Do lymph vessels contain valves?
Yes
Where do lymphatic vessels take lymph?
To nodes for immune surveillance
Back to blood stream at veins at root of neck
How is lymph moved through the lymphatic system?
Via
- smooth muscle in vessel walls
- hydrostatic pressure in tissue
- compression of vessels by voluntary muscles
- valves
How is lymph moved through the lymphatic system?
Via
- smooth muscle in vessel walls
- hydrostatic pressure in tissue
- compression of vessels by voluntary muscles
- valves
How much blood does the average adult have?
4.5 - 6 litres
What is serum?
substance in blood obtained by the centrifugation of blood from which the clotting factors have been removed
What happens to the components of blood if spun in a centrifuge?
Plasma/serum found at top
White cells next
Red blood cells at bottom
What happens to an erythrocyte after 4 months?
Removed from circulation by spleen and liver
What is a neutrophil and what is it’s function?
Type of granulocyte - contains many granules which are difficult to stain with either basic or acidic dyes
Most common leukocyte
Multi-lobed nucleus
Inactive in circulation, activated by presence of pathogen/inflammation, they move into tissue and act as highly motile phagocytes
Short-lived, production in bone marrow high
Describe eosinophils
Granulocytes with affinity for red acidic dye eosin
Bilobed nucleus
Slightly larger than neutrophils
Describe the function of esosinophils
Released from marrow and circulate for 8-12 hours, then move into tissue (especially spleen, lymph nodes, and GI tract) and live there
Their granules contain hydrolytic enzymes
Important in initiation and maintenance of inflammation (allergic reaction, asthma) and fighting parasitic infection
Describe basophils
Rarest of granulocytes
High affinity for basic dyes such as methylene blue, stains them purple/blue
Bilobed nucleus, often obscured by granules
Granules contain heparin, histamine, and other inflammatory mediators
What do basophils do?
They are Effector cells during allergic reactions
When a specific allergen binds to their IgE receptors, the granules are released (degranulation)
Leads to allergic reaction eg hayfever, allergic asthma, allergic dermatitis
What is the mononuclear phagocyte system?
monocytes and macrophages
Where are macrophages found?
Everywhere but especially in loose connective tissue
Describe a monocyte
Is an agranulocyte, contain many small lysosomal granules
Describe a monocyte
Is an agranulocyte, contain many small lysosomal granules
Largest blood cell
Non-lobulated nucleus, nucleus kidney-bean shape
Name three members of the mononuclear phagocytic system which do not move around the body
Kupffer cells in liver
Microglia in brain
Langerhan’s cells in skin
Do lymphocytes contain granules?
No, they are agranulocytes
Describe the nucleus of a lymphocyte
Round
What do B and T cells have in common?
Appear identical in normal staining, no granules, arise in bone marrow, involved in specific immune response
T cells differentiate in thymus
What is the function of a B cell?
Produce antibody secreting plasma cells
What is the function of a T cell?
Defending against infection
Inducing apoptosis
Aiding other immune cells
When are the first erythrocytes made?
At 3 weeks (within womb) in yolk sac
What is hemopoiesis?
the production of blood cells
During the 2nd trimester, where is most of the blood formed?
Liver
Some hemopoeitic cells in spleen
After birth, where is the main site of blood production?
Bone marrow
Baby - all bones
Adult - Full (Femur) Sleepy (skull) Hippos (hip) Happily (humerus) Rest (rib) Very (vertebrae) Still (sternum)
Marrow in other bones contains adipose cells but can making blood if necessary
What are megakaryocytes?
Very large cells (30 to 100 micrometers) which produce platelets in bone marrow
Duplicates nuclear material but never divides nucleus/cell - nucleus is huge
Platelets are fragments separated from periphery of cell
Where are continuous capillaries found?
muscle, nerves, lungs, and skin
Where are fenestrated capillaries found?
gut mucosa, endocrine glands, and kidneys
Where are discontinuous/sinusoidal capillaries found?
liver, spleen, and bone marrow
Describe the structure of an erythrocyte
Biconcave discs, no nucleus and no organelles, 33.3% of volume is haemoglobin
How big is an erythrocyte?
7 micrometers
Why can an erythrocyte squeeze through a gap smaller than itself?
Flexible cytoskeleton