Blood Flashcards
What is the 3 basic layer of blood vessels?
Tunica intima
Tunica media
Tunica adventitia
What makes up the tunica intima?
Single layer of squamous epithelial cells - endothelial cells
Supported by a basal lamina and thin layer of connective tissue
What makes up the tunica media?
Predominately smooth muscle
Thickness of layer varies
What makes up the tunica adventitia?
Supporting connective tissue
What separates the tunica layers?
Internal elastic membrane separates TI from TM
External elastic membrane separates TM frrom TA
What are the three types of capillaries?
Continuous
Fenestrated
Discontinuous
What are capillaries made of?
Endothelial cell
Basal lamina
Where do capillaries drain?
Post-capillary venules
What are post-capillary venules made of?
Endothelial cell lines
Thin layer of connective tissue
What changes a post-capillary venule to a venule?
When the vessel begins to acquire intermittent smooth muscle in the tunica media
Structure of veins
Normal tunica intima
Thin but continuous tunica media, consisting of a few layers of smooth muscle
An obvious tunica adventitia
Structure of artery
Thick tunica media
What is blood made up of?
45% formed elements
55% plasma
What makes up plasma?
90% water
proteins
nutrients
salts
What makes up the formed elements?
Red Cells
White cells
Platelets
What types of white cells are present in the blood?
Granulocytes - neutrophils, eosinophils, basophils
Agranulocytes - lymphocytes, monocytes
How can blood be separated?
Spinning in a centrifuge
Red cells are densest so are found at bottom after spinning
White cells next and plasma on top
Where are most proteins in the blood produced?
What are they?
Liver
Serum albumin, clotting factors and complement components
What are the roles of albumin?
Maintain osmotic pressure
Structure of erythrocytes
Biconcave discs
7 microns in diameter
Why are mature erythrocytes not true cells?
They have no nucleus or organelles
Strucutre of mature erythrocytes
1/3 volume haemoglobin
Contain a network of flexible cytoskeletal elements allowing them to deform and slip through spaces smaller than themselves
Mammalian erythrocytes lack nuclei
Non-mammalian vertebrates have nuclei
What is the role of haemoglobin?
In the lungs it picks up oxygen to become oxyhaemoglobin
Delivers the oxygen to the tissues
How is carbon dioxide transported back to lungs?
70% dissolved in the plasma
30% bound to haemoglobin
How long do erythrocytes last in circulation?
Approx 4 months
Removed by spleen and liver
What is a rouleau?
A stack of erythrocytes
May indicate disease
Proportions of white blood cells
neutrophils - 40-75% eosinophils - 5% basophils - 0.5% lymphocytes - 20-50% monocytes - 1-5%
Structure of neutrophils
Cytoplasm contains mainly granules
Prominent, multi-lobed nucleus = polymorphonuclear leukocytes
What is the role of neutrophils?
Circulate in an inactive state
Stimulated by presence of bacteria or inflammation
Enter the tissue as highly motile phagocytes that ingest bacteria or damaged cells
Abundant and short-lived which means that a significant portion of bone marrow is devoted to their production
Role of eosinophils
Released from marrow and circulate for 8-12 hours
Then move into tissue (spleen, lymph nodes and GI tract) where most eosinophils live
Induce and maintain inflammation, particularly in allergic reactions and asthma
Also fight parasitic infection
Structure of eosinophils
Slightly larger than neutrophils
Bilobed nucleus
Structure of basophils
Prominent granules in cytoplasm
Bilobed nucleus but often obscured by granules
Role of basophils
Act as effector cells in allergic reactions
Directed against particular allergens and bind their antigen to stimulate granule release
Leads to hayfever, allergic asthma or dermatitis
What cells are basophils similar to?
Mast cells
Structure of monocytes
Found in bone marrow and blood
Numerous small lysosomal granules
Largest cells circulating in blood, particularly found in loose connective tissue
Non-lobulated nucleus which often appears as kidney bean shaped
Role of monocytes
Serve as precursors of tissue macrophages
Together they form the mononuclear phagocyte system
What members of the mononuclear phagocytic system remain resident in particular tissues?
Kupffer cells in the liver
Microglia in the brain
Structure of lymphocytes
Round nucleus surrounded by a thin rim of cytoplasm with no visible granules
Two classes - B cells and T cells
Role of lymphocytes
Participate in specific immune response
B cells give rise to antibody secreting plasma cells
T cells form a complex set of cells that perform many defense functions
What are platelets?
Small cell fragments about 2 microns in diamter
Found in large numbers in blood
Play a key role in homeostasis
Role of platelets
Hemostasis - platelets adhere to the site of damage, aggregate and degranulate
Activate production of fibrin which participates in clot formation
Where is the earliest site of erythrocyte formation during development?
Outside the embryo in the yolk sac about 3 weeks gestation
Where is the principal site of blood formation in the second trimester?
Liver
Where is the main site of blood formation by birth?
Bone marrow
As bones enlarge during growth, there is excess capacity so hemopoiesis is shut down in many bones
By skeletal maturity, where retains hemopoiesis?
Vertebrae Ribs Skull Pelvis Proximal femurs
What are the four classes of stem cells?
Totipotent
Pluripotent
Multipotent
Committed progenitor cells
Can all reproduce themselves, maintaining the pool of stem cells
Function of totipotent stem cells
Form all cell types of the adult plus any extra embryonic tissue produced during development
e.g - fertilised ovum
Function of pluripotent stem cells
Give rise to all functional cell types of the animal
e.g. - embryonic stem cells, hemopoietic stem cells
Function of multipotent stem cells
Give rise to a restricted set of cell types
e.g. - lymphoid stem cells
Function of committed progenitor cells
Can produce only one cell type
e.g. - CFU-E cells produce only erythrocytes
What are megakaryocytes?
Giant cells found in bone marrow
What controls the production of blood cells in the bone marrow?
A complex set of growth factors and hrmones
What do locally produced growth promoters include?
Several colony stimulating factors
What do systemic factors include?
Several of the interleukins produced by leukocytes
What does erythropoietin stimulate and where is it produced?
Produced in kidney
Stimulates erythrocyte production
What are the 3 stages of blood cell production?
Proliferation
Differentiation
Maturation
What do the granules of neutrophils contain?
Numerous enzymes and microbicidal agents
What do the granules of eosinophils contain?
A variety of hydrolytic enzymes and they have a variety of surface receptors
What do the granules of basophils contain?
Histamine, heparin and other inflammatory mediators
What is a reticulocyte?
An erythrocyte after it develops and matures through steps that include production of haemoglobin and extrusion of the nucleus
Why is termed a reticulocyte?
Because of the granules of RNA in their cytoplasm
How long do reticulocytes last?
They circulate for 1-2 days in the blood stream before RNA is lost and a mature RBC is formed
What is the blood brain barrier induced by?
Astrocytes (induced by, not formed by)
