Arteries And Veins Flashcards
Structure of arteries and veins
Tunica intima, tunica media, tunica externa
Lumen of arteries, veins and capillaries
Central blood containing space (hole of the vessel)
Tunica intima is made of
Endothelium lines the lumen of all vessels. In vessels larger than 1mm a subendothelial connective tissue basement membrane is present
Tunica media is made if
Smooth muscle and sheets of elastin.
Sympathetic gasometer nerve fibres control vasoconstriction and vasodilation of vessels
Tunica externa (Tunica Adventitia) is made of
Collagen fibres protecting and reinforcing the vessel.
Larger vessels contain vasa Vado rum to nourish external layer
What are Elastic (conducting) arteries?
Large thick-walled arteries with elastin in all three tunics.
Large lumen offers low resistance.
Which arteries are the elastic arteries?
Aorta and it’s major branches, pulmonary trunk
What do elastic arteries act as?
Act as pressure reservoirs, expanding and recoiling as blood is ejected from the heart
What is distal to the elastic arteries?
The muscular (distributing) arteries and arterioles
What are muscular (distributing) arteries and arterioles?
Deliver blood to body organs, have thick tunica media with more smooth muscle. Active in vasoconstriction
Are the muscular (distributing) arteries or elastic (conducting) arteries active in vasoconstriction?
Muscular (distributing) arteries
What are arterioles?
The smallest arteries that lead to capillary beds.
What do arterioles do?
Control flow into capillary beds via vasodilation and vasoconstriction
Capillaries are
Microscopic blood vessels with walls of this tunica intima and are one cell thick.
Pericytes help stabilise their walls and control permeability
Size only allows one RBC to pass at a time
Capillary function:
Exchange of gases, nutrients, wastes, hormones etc
Why do tendons and ligaments heal slowly?
Poorly vascularised, not many capillaries present
Capillaries are present in all tissues except
Cartilage
Epithelia
Cornea
Lens of eye
What are venules and how are they formed?
Formed when capillary beds unite.
Very porous which allows fluids and white blood cells j to tissues
Larger venules have one or two layers of smooth muscle cells
What do postcapillary venules consist of?
Consist of endothelium and a few pericytes
Veins are formed
When venules converge
Veins have
Thinner walls, larger linens compared with corresponding arteries.
Have lower BP
Thin tunica media and a thick tunica externa consisting of collagen fibres and elastic networks
What are capacitance vessels (blood reservoirs) because
Veins contain up to 65% of blood supply
How do veins return blood to heart from body?
Large diameter lumens offer little resistance
Valves prevent backflow
Valves in veins are most abundant where?
In veins of the limbs
Venous sinuses are what?
Flattened veins with extremely thin walls (eg coronary sinus of the heat and rural sinuses of the brain)
Vascular anastomoses are
The interconnections of blood vessels
Vascular anastomoses provide
Alternate pathways (collateral channels) to a given body region, common at joins, in abdominal organs, brain and hearr
What is an example of an arteriovenous anastomoses?
Vascular shunts
Cardiac muscles look like what?
Striated cells that are short, fat, branched and interconnected
In which muscle cell are the T-tubules wide but less numerous? SR is also very simple
Cardiac muscle.
Numerous mitochondria per cell can be found in which muscle cell?
Cardiac muscle
What are intercalated discs and where are they?
Found in muscle cells, they are the junctions between cells that anchor cardiac cells
Desmosomes prevent
Prevent cells from separating during contraction
Gap junctions in cardiac muscle allow
Allow ions to pass, electrically couple adjacent cells
True or false: the heart muscle behaves as a functional syncytium
True
What is blood?
A fluid connective tissue
What is blood composed of
Plasma
Formed elements such as: erythrocytes (RBCs), Leukocytes (WBCs) and platelets
Hematocrit is what?
The percent of blood volume that is RBCs (42% in females, 47% in males)
When blood is dark red this indicates what?
Blood is oxygen poor. Should look scarlet when oxygen rich
True or false: Blood is not more viscous than water
False because:
Higher the hematocrit the more viscous and greater resistance to flow
Is blood alkaline or acidic?
Slightly alkaline: pH 7.35-7.45
How many litres of blood?
5-6 L for males and 4-5 L for females
Functions of blood in distribution and transportation
Carries O2 to body cells, carried metabolic wastes to the lungs and kidneys for elimination.
Carries hormones from endocrine organs to target organs
Function of blood in regulation
Regulates body temperature by absorbing and distributing heat. Maintains normal pH using buffers
Function of blood in protection against blood loss and infection
Plasma proteins and platelets initiate clot formation to prevent loss of blood
Blood Carrie’s antibodies and WBCs which defend against foreign invaders
Blood plasma is 90%
Water
Proteins found in blood from
Liver
60% albumin
36% globulins
4% fibrinogens
Albumins are carriers of
Molecules, hormones, and are the main contributor of colloid osmotic pressure
Globulins transport what
Proteins that bind to lipids, metal ions and fat soluble vitamins
Fibrinogen helps form
Fibrin bridges between platelets to help clot blood
Blood plasma also carries
Nitrogenous by products of metabolism such as lactic acid, urea, creatinine. Nutrients Electrolytes Respiratory gases Hormones
True or false: WBCs aren’t complete cells
False. Only RBCs are incomplete as they have no nuclei or organelles. Platelets are cell fragments
How are blood cells made?
Via stem cells in red bone marrow which divide continuously to produce more blood cells
Erythrocytes (RBCs) look like
Biconcave discs, no nucleus and essentially no organelles.
Erythrocytes are filled with
Haemoglobin for gas transport.
What is a major contributor to blood viscosity?
Erythrocytes RBCs
Red blood cells generate ATP via
Anaerobic mechanisms
True or false: RBCs are dedicated to respiratory gas transport
True and the haemoglobin binds reversibly with oxygen.
Haemoglobin structure
Protein globin
Heme pigmen
Can an iron atom present in each heme of a Hb bind to more than one O2 molecule?
No. Can only bind to the one
How many O2 molecules can a Hb transport?
4
O2 loading in the lungs produces
Oxyhemoglobin
O2 unloading in the tissues produces
Deoxyhemoglobin or reduced Haemoglobin
CO2 loading in the tissues produces
Carbaminohemoglobin
Haematopoiesis is the process of
Blood cell formation
Harmatopoiesis occurs in
Occurs in red bone marrow of axial skeleton, girdles and proximal epiphyses of humerus and femur
Hemocytoblasts are what
Haematopoietic stem cells and give rise to all formed elements.
Erythropoiesis is the production of
Red blood cells
Tissue hypoxia occurs because
Too few RBCs
An increase in blood viscosity occurs when
Too many RBCs present
Balance between RBC production and destruction depends on
Hormonal controls
Adequate supplies of iron
Erythropoietin (EPO) hormone is the
Direct stimulus for erythropoiesis. This hormone is Released by the kidneys in response to hypoxia
Hypoxia is caused by
Hemorrhage (bleeding)
Insufficient Haemoglobin (iron deficiency)
Reduced availability of O2
Effects of EPO (erythropoietin
More rapid maturation of commuted bone marrow cells and increased circulating reticulocyte count in 1-2 days.
Testosterone enhances which RBCs hormone regulator
EPO- erythropoietin
What happens to erythrocytes after 100-120 days?
The RBCs become old and fragile and Hb begins to degenerate inside them. Macrophages engulf dying RBCs in spleen
How are macrophages produced?
Circulating monocytes leave the bloodstream to enter tissues and differentiate into macrophages
