Circulatory system

Question 1

what does the blood vascular system consist of?

Answer 1

it consists of the heart, arteries, arterioles, capillaries, venules and veins.

Question 2

describe generally the heart…

Answer 2

the heart is made up of 4 muscular chambers, two atria and two ventricles. the chambers are surrounded by a fibroserous sac - the pericardium.

the heart receives sympathetic and parasympathetic inervation, which modulate but do not initiate the rate of the heartbeat.

Question 3

what hormone doe the heart produce to control blood pressure?
- how is this control executed?

Answer 3

the heart produces atrial natriuretic peptide
the hormone increases sodium and water secretion by the kidneys, and inhibits the release of renin, both of which decrease blood pressure.

Question 4

what are the cardiac layers of the heart?

Answer 4

1. endocardium
2. myocardium
3. epicardium

Question 5

what is endocardium?

Answer 5

endocardium lines the lumen of the heart with simple squamous epithelium and a thin layer of loose connective tissue.
the subendocrdium underlies the endocardium and contains veins, nerves and purkuinje fibres in a connective tissue layer.

Question 6

what is the myocardium?

Answer 6

derived from splanchnic mesoderm, the myocardium is the muscular layer of the heart.
the muscle cells are arranged in a spiral fashion about the hearts chamberes and inserted into the fibrous skeleton.
the myocardium contracts to expel blood from the heart into the arteries for distribution.

Question 7

what hormones do the specialised cardiac cells of the atria of the heart produce?

Answer 7

atria natruretic polypeptide, atriopeptin, cardiodilatin,

all hormones that maintain flud and electrolyte balance and decrease blood pressure.

Question 8

what is the epicardium?

Answer 8

the epicardium os the outermost lining of the heart - the visceral layer of the pericardium.

outer simple squamous epithelium (mesothelium) lines inner fibroelastic connective tissue containing nerves and coronary vessels as well as adipose tissue.

Question 9

what is the fibrous skeleton of the heart?

Answer 9

the fibrous skeleton is made of thick bundles of collagn fibres orientated in various directions.

it is there for support and eshtablished electrically impermeable boundries to autonomic influence within the heart.

Question 10

what are the two types of heart valves?

Answer 10

1. AtrioVentricular valves (AV)

2. semilunar valves

Question 11

what are the two AV valves formed from?

- function

Answer 11

the AV valves are composed of a skeleton of fibrous connective tissue arranged like aponeurosis and lined by endothelium on both sides.

they attach to the annuli fibrosi of the fibrous skeleton

the right has 3 cusps (tricuspid valve)
the left has 2 cusps (bicuspid mitral valve)

the valves prevent backflow of blood from the ventricles into the atria.

Question 12

what are the semilunar valves composed of?

- function

Answer 12

the semilunar valves are found in the pulmonary trunk and the aortic trunk.
each is composed of 3 cusps that when filled pushed towards each other, closing the vessel.
they are lines by endothelium on both sides separated by sparse strands of connective tissue

the valves prevent regurgitation of blood back into the ventricles in which it came.

Question 13

what is the impulse path that initiates and regulates heartbeat?

Answer 13

SA node generates impulses that initiates contraction of the atrial muscle.

impulses are conducted to the AV node

then down the AV bundle of His in the interventricular septum where it divides into branches and continues as purkinje fibres.

Question 14

where is the SA node of the heart located?

Answer 14

the SA node is the pacemaker of the heart composed of specialised cardiac cells located in the wall of the right atrium.

Question 15

where is the AV node of the heart?

Answer 15

the AV node is located in the wall of the right atrium, adjacent to the tricuspid valve.

Question 16

what purkinje fibres?

Answer 16

purkinje fibres are large modified cardiac muscle cells that make contact with cardiac muscle cells in the apex of the heart via gap junctions, desmosomes and fasciae adherentes

Question 17

what is the purfpose of the ANS in the regulation of the heart beat?

Answer 17

the ANS modulates but does not generate the impulse that controls the heart rate and stroke volume.

sympathetic innervation accelerates the heart rate

parasympathetic innervation slows heart rate.

Question 18

what is the function of arteries?

Answer 18

arteries conduct blood away from the heart to organs and tissues of the body.

Question 19

what are the layers the compose arteries?

Answer 19

1. tunica intima - inner layer
2. tunica media - middle layer
3. tunica adventitia - outer layer

Question 20

what are the types of arteries?

Answer 20

1. elastic arteries (conducting arteries)
2. muscular arteries (distributing arteries)
3. arterioles
4. metarterioles

Question 21

what are elastic arteries?

Answer 21

elastic arteries are large conducting arteries. mostly aorta and its major branches.

• elastic arteries help reduce blood pressure associated with heartbeat.
• small vessels (vasa vasorum) and nerves run in their tunica adventitia and tunica media.
• thick, concentric sheets of elastic membrane (fenestrated) are found in their tunica media.

Question 22

what are muscular arteries?

Answer 22

muscular arteries are distributing arteries. they include mostly the named arteries of the body.

• medium in size (between elastic arteries and arterioles)
• tunica adventitia contains vaso vasorum
• tunica media is thick, composed of layer of smooth muscle larger muscular arteries. and possesses an external lamina separating their boundry with the tunica adventitia.

Question 23

what are arterioles?

Answer 23

arterioles regulate blood pressue and are terminal arterial vessels. they are the smallest of arteries with diameters of less that 0.1mm.

• they have narrow lumen
  - lumen size = wall size
• tunica adventitia is scant
• tunica media is composed of two layers of smooth muscle cells
• tunica intima consists of endothelium, a basal lamina and scant connective tissue

Question 24

what are metarterioles?

Answer 24

metarterioles are narrow vessels arising from arterioles and give rise to capillaries.

• surrounded by incomplete sings of smooth muscle cells
• possess single smooth muscle cells that surround the origin to capillaries (precapillary sphincter)
• the precapillary sphincter prevents blood flow into the capillary bed.

Question 25

what is vasocontriction?

Answer 25

vasoconstriction primarily involves arterioles and reduces flow to a local region. - stimulated by sympathetic innervation via vasomotor nerves. - nerves DO NOT synapse onto the smooth muscle cells, however discharge the neurotransmitter norepinephrine that diffuses through the smooth muscle layers and induces contration of cells via gap junctions - reducing the luminal diameter of the arteriole.

Question 26

what is vasodilation?

Answer 26

vasodilation is accomplished via parasympathetic innervation. - nerve terminals secrete acetylcholine, whcih stimulated the endothelium to release nitric oxide (EDRF) - nitric oxide diffused across the smooth muscle cells in the vessel wal and activates their cGMP system, resulting in relaxation, which dilates the lumen

Question 27

what is the general structure of a capillary?

Answer 27

capillaries consist of a single layer of endothelial cells arranged as a continuum to form a cylinder, surrounded by a basal lamina and occasional pericytes. the endothelial cells: - are nucleated, polygonal cells with attenuated cytoplasm - posses golgi complex, ribosomes, mitochondria, and some RER - contain IF (desmin and vimentin) supportive function - joined by tight junctions - luminal diameter may only hold 1 RBC at a time

Question 28

how can capillaries be classified?

Answer 28

1. continuous (somatic) capillaries 2. fenestrated (visceral) capillaries 3. sinusoidal (discontinuous) capillaries

Question 29

what are continuous capillaries?

Answer 29

located in nervous tissue, muscle, connective tissue, exocrine glands and lungs continuous or somatic capillaries lack fenestrae and have a continuous basal lamina. they contain numberous pinocytic vesicles (except in CNS)

Question 30

what are fenestrated capillaries?

Answer 30

located in endocrine glands, intestine, pancreas and glomeruli of kidneys fenestrated or visceral capillaries contain an endothelial cells that are perforated with fenestrae. - opening are 60-80nm and bridged by a diaphragm (except in glomeruli) they have a continuous basal lamina

Question 31

what are sinusoidal capillaried?

Answer 31

located in the liver, spleen, bone marrow, lymph nodes and adrenal cortex, sinusoidal or discontinuous capillaries possess many fenestrae that lack diaphragms. sinusoidal capillaries are larger than continuous and fenestrated capillaries with a diameter of 30-40nm these capillaries DO NOT have a continuous basal lamina.

Question 32

what is diapedesis?

Answer 32

diapedesis is the process of leukocytes leaving capillaries via intercellular junctions to enter surrounding tissue.

Question 33

what are the metabolic functions of capillaries? (7)

Answer 33

1. conversion: angiotensin I to angiotensin II 2. deactivation: bradykinin, serotonin, thrombin... 3. breakdown of lipoproteins 4. release of prostacyclin - potent vasodilator 5. release of NO and Endothelin I 6. regulation of transendothelial migration (neutrophils) 7. release of tissue factors >> blood coagulation

Question 34

what two ways can blood bypass a capillary bed from arterioles?

Answer 34

1. contraction of precapillary sphincters prevent blood flow into the capilary bed from metarterioles, thus diverting the blood through a throughfare channel connected directly to a small venule 2. AV anastomoses are small vessels that directly connects arterioles to venules.

Question 35

what are veins?

Answer 35

veins conduct blood from tisuees towards to the heart. veins contain ~70% of bodys blood at any one time. the walls of veins are composed of 3 layers: 1. tunica intima 2. tunica media 3. tunica adventitia (thickest and most prominent) vaso vasorum are more numerous in veins than arteries no distinct elastic lamina in veins.

Question 36

what does the lymphatic vascular system consist of?

Answer 36

it consists of peripheral lymphatic vessels, lymphatic vessels of gradually increasing size, and lymphatic ducts.

Question 37

what is the purpose of the lymphatic vascularture?

Answer 37

it collects excess tissue fluid (lymph) and returns it to the venous portion of the cardiovascular system. it drains most tissue (except the nervous system and bone marrow)