Week 8 - Blood & Blood Vessels Flashcards
What are the main types of bv
Arteries
Arterioles
Capillaries
Venules
Veins
Define vascular tone
Ability of muscle in vessels to contract + maintain a state of partial contraction.
– Important in maintaining vessel pressure + efficient bf.
Where does microcirculation occur
Arterioles
Capillaries
Venules
List the Tunics of a bv
Tunica interna / intima
Tunica Media
Tunica Externa / Adventitia
Whats on the inner most layer of the tunica interna / intima
Endothelium – Thin layer of flattened cells
What on the the tunica interna facilitates efficient bf by ⬇️ surface tension?
Smooth luminal surface
What is deep to the endothelium on the tunica intima / interna
Basement membrane
What does the basement membrane of the tunica interna do?
Provides physical support for the epithelial layer.
Anchors endothelium, to underlying connective tissue
+ regulates molecular movement.
What is the most outer part of the tunica interna?
Internal elastic lamina
= Thin sheet of elastic fibres w/ a no. of window like openings to facilitate diffusion.
Describe the tunica media
Muscular + connective tissue of mainly smooth muscle + lots of elastic fibres.
What is the role of the smooth muscle in the tunica media
Reg. diameter of lumen via vasoconstriction/dilation.
Also contracts when a small artery or arteries are damaged to help limit loss of blood.
What does the tunica externa consist of
Elastic + collagen fibres.
Nerves, tiny bv + lymphatics
What are the vasa vasorum
Small vessels that supply blood to the tissues of the tunica externa.
What are the 2 types of arteries
Elastic
Muscular
Examples of elastic arteries
Aorta + pulmonary trunk
Both conducting arteries
What is the function of the aorta + pulmonary trunk in being elastic arteries
Propel blood onward while ventricles are relaxing.
What is meant by the elastic arteries functioning as a pressure reservoir
Their walls stretch to accommodate surge of blood = elastic fibres momentarily store mechanical energy.
Fibres recoil + convert pot. energy into KE of the blood
If elastic arteries are known as conducting arteries, what are muscular arteries known as?
Distributing arteries
– Distribute blood to arterioles
Tunica interna of arterioles
Thin
Fenestrated internal elastic lamina that disappears distally.
Tunica media of arterioles
1-2 layers of circular smooth muscle
– Form precapillary sphincters at distal end
Tunica externa of arterioles
Loose collagenous connective tissue
Unmyelinated sympathetic nerves
What part of the arteriole has the precapillary sphincters
Metarteriole
Where the metarteriole-capillary junction is formed
Function of arterioles
Regulate blood flow into cap. networks
What causes resistance to blood flow in bv
Friction between blood + inner walls of bv.
Tunica interna of capillaries
Endothelium + basement membrane.
No tunica media or externa
Tunica interna of postcapillary venules
Endothelium + basement membrane.
No tunica media + tunica externa is sparse.
Tunica interna of muscular venules
Endothelium + basement membrane
Tunica media of muscular venules
1-2 layers of circular smooth muscle.
Tunica externa - sparse.
What do muscular venules do?
Act as reservoirs for accumulating large vol. of blood.
Tunica interna for veins
Endothelium + basement membrane.
Valves
Large lumen
Does the tunica interna of the veins contain internal elastic lamina?
NO
Tunica media for veins
Thinner than arteries
Does the tunica media of veins have an external elastic lamina
NO
Tunica externa of the veins
Thickest layer
Collagen + elastin
what happens at the capillaries
Exchange of substances between blood + interstitial fluid
What stabilises the walls of the capillaries
Pericytes
What are the 3 types of capillaries
Fenestrated
Sinusoid
Continuous
Define capillary bed
Network of 10-100 capillaries that arises from a single metarteriole
Define vasomotor
Intermittent contraction + reaction occurring 5-10 times/min
Where can fenestrated capillaries be found?
Where active capillary absorption / filtration occurs
i.e
Kidneys, small intestine + endocrine glands
What do the fenestrated capillaries have
Endothelium w/ pores
== Greater permeability
Properties of the sinusoid capillaries
Highly modified + leaky
Large lumen
Large mol. can pass through
Sluggish bf
Where can the sinusoid capillaries be found
Liver
Bone marrow
Spleen
Where are the continuous capillaries abundant?
Skin + muscle
Describe the continuous capillaries in the brain
Tight junctions around endothelium
Make up blood-brain barrier
Define vascular sinus
Vein w/ thin endothelial wall + no smooth muscle to alter its diameter
What are the functions of the blood
Transportation — Gases, nutrients, waste
Regulation — pH, body temp, osmotic balance
Protection — Clotting, immunity
Describe plasma
Straw-coloured liquid
About 91.5% H20
8.5% solutes
What %, by weight, are proteins of the solutes?
7%
What is the function of water in the plasma
Solvent + suspending medium
Absorbs, transports + releases heat.
List the plasma proteins
Albumins
Globulins
Fibrinogen
Function of plasma proteins
Responsible for colloid osmotic pressure.
Contributors to blood viscosity.
Transports hormones, fatty acids + Ca2+.
Helps reg. blood pH
Function of electrolytes in blood plasma
Maintains osmotic pressure
Essential roles in cell functions
What reg. no. of RBCs + platelets in circulation?
-ive fb systems
What does the abundance in types of WBCs vary according to?
Challenges by invading pathogens + other foreign antigens.
Define hemopoiesis / hematopoiesis
Process by which formed elements of blood develop.
Primary sit in red bone marrow in last 3 months before birth + throughout life.
Define red bone marrow
Highly vascularised connective tissue in microscopic spaces between trabeculae of spongy bone.
What % of red bone marrow cells are pluripotent stem cells / hemocytoblasts ?
Where are they derived from?
0.05-0.1%
Mesenchyme
How many RBCs enter blood stream per sec
2 million
Plasma membrane of RBCs
Strong + flexible
== Allows them to deform w/.out rupturing as they squeeze through narrow blood capillaries.
Diameter of RBCs
7-8 micrometers
What % of the blood is whole blood + then other fluids + tissues
Whole blood - 8%
Other - 92%
How long do RBCS last + why
About 120 days due to wear + tear of plasma membranes
What is erythropoiesis
RBC prod.
What is hypoxia
Low blood O2
Where is EPO released from
Kidneys
What does erythropoiesis start with
Proerythroblasts
What do the pro erythroblasts do
Eject the nucleus to allow space to carry O2 in which a reticulocyte is formed.
What happens to the reticulocyte?
Escapes from bone marrow
+ in 1-2 days after it ejects other organelles to become a MATURE RBC.
What are the average hematocrit levels
42%
What does it mean if the hematocrit levels are above 50%?
Athlete has doped
Do WBCs have a nuclei
YES
What are the classifications pithing WBCs
Granular
Agranular
(Depending on whether they contain vesicles)
What are the 5 types of WBCs
Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophil
Give examples of granular WBCs
Neutrophils
Basophils
Give examples of granular WBCs
Lymphocytes
Monocytes
How long do platelets function for
10 days
Do platelets have nuclei
NO
In what ways are platelets involved in clotting
Adhesion
Activation
Aggregation
Serum
Blood plasma minus clotting proteins
Blood clot
Consists of a network of insoluble protein fibres called fibrin in which the formed elements of blood are trapped.
What could be the result of blood clotting too easily
Thrombosis
What could be the result of blood taking too long to clot
Haemorrhage
Stages of blood clotting
- Intrinsic + extrinsic pathways lead to formation of pro-thrombinase. - Once formed, the next 2 stages are the same for both intrinsic + extrinsic pathways + referred to as COMMON Pathway.
- Pro-thrombinase converts prothrombin –> enzyme thrombin.
- Thrombonin converts soluble fibrinogen into insoluble fibrin – forming threads of the clot.
What is the extrinsic pathway in blood clotting for
Tissue trauma
What is the extrinsic pathway in blood clotting for
Activators are either in direct contract w/ blood or contained w/in blood.
What happens in the extrinsic pathway of blood clotting
Thromboplastin leaks into blood from cells outside of bv + initiates formation of prothrombinase.
What is thromboplastin?
Complex mixture of lipoproteins + PL released from the surfaces of damaged cells.
What does thromboplastin do in the presence of Ca2+?
Begins a sequence of reactions that activates clotting factor X.
Once activated, combines w/ factor V to form prothrombinase.
= completing the extrinsic pathway.
What happens in the intrinsic pathway of blood clotting
If endothelial cells become damaged, blood can come into contact w/ collagen fibres in the connective tissue around the endothelium of the bv.
Trauma to endothelial cells causes damage to platelets, resulting in release of PL.
Contact w/ collagen fibres activates clotting factor XII which starts a seq. of reactions that eventually activate clotting factor X.
- Once activated, combines w/ factor V to form prothrombinase, completing the intrinsic pathway.
Which is faster, the intrinsic or extrinsic pathway in blood clotting
Extrinsic
What happens in the common pathway of blood clotting
Prothrombinase + Ca2+ catalyse conversion of prothrombin –> thrombin.
In presence of Ca2+, thrombin converts fibrinogen, soluble, to loose fibrin threads, insoluble.
Thrombin also activates factor XIII which strengthens + stabilises fibrin threads into a sturdy clot. Plasma contains some factor XIII which is also released by platelets in clot.
What are the 2 +ive fb effects of thrombin
Thrombin accelerates formation of prothrombinase = accelerates prod. Of more thrombin…
Thrombin activates platelets which reinforces their aggregation + the release of platelet PL.
Clot retraction happens after the common pathway, describe what happens
Once clot is formed, it plugs ruptured area of bv.
= Tightening of fibrin clot.
Fibrin threads attached to damaged surfaces of bv gradually contract as platelets pull on them.
As clot retracts, it pulls edges of damaged vessel closer together, decr risk of further damage.
Some serum can escape between fibrin threads during retraction but the formed elements in blood can’t.
What do the surfaces of erythrocytes contain?
A genetically determined assortment of antigens composed of glycoproteins + glycolipids.
How many blood groups are there
At least 24
How many antigens are there that can be detected on the surface of RBCs
100+
What are blood groups based on
2 glycolipid antigens called A + B
What blood can type A people receive
Type A + O blood
What blood can type B people receive
Type B + O
What blood can type AB people receive
A, B, O + AB
What blood can type O people receive
Type O
Rhesus factor
+ive or -ive
+ive = Accept +ive or -ive
-ive = Accept ONLY +ive
Which blood is a universal acceptor
AB +
Which blood is a universal donor
O-
How does the basement membrane of the tunica interna provide physical support for the epithelial layer?
Collagen fibres allow sig. tensile strength, resilience for stretching + recoil.
