week 7 Cardiovascular and Lymphatic System Flashcards

Flashcards about the cardiovascular and lymphatic system

Function of the cardiovascular system

Transportation, maintenance of homeostasis, protection.

Blood

A liquid connective tissue, consists of plasma (55%) and formed elements (45%), constant formation of blood cells (haematopoiesis).

Order of blood vessels

arteries and arterioles take the blood away from the heart (usually oxygenated). Capillaries are the site of exchange. Veins and venules take the blood away from the tissue to the heart (usually deoxygenated).  Arteries, arterioles, capillaries, venules, veins      

Layers of blood vessels (inside out)

1. Tunica intima- (endothelial layer, basement membrane, internal elastic lamina) 2. Tunica media- (smooth muscle, external elastic lamina) 3. Tunica externa- (connective tissue)

Structure and function of arteries

Contains the three tunica layers, large diameter and thick walls, thick tunica media that aids elasticity and contractability to maintain pressure and tone.

Structure and function of arterioles

Contains three tunica layers (the smallest vessels containing all three), thick walls relative to lumen size, and regulates blood flow into capillaries.

Structure and function of capillaries

consists only of an endothelial layer and a basement membrane to allow the exchange of substances. Capillaries form a network called capillary beds.  There are 3 different types of structures. 1 continuous: no gaps, tight junctions between cells 2. Fenestrated: the endothelial cell membrane has small holes 3. Sinusoid: large and numerous fenestrations with an incomplete basement membrane

Structure and function of venules

The tunica layers depend on the type of venule; it drains the capillaries and begins to return the flow to the heart.

Structure and function of veins

Contains all three tunica layers, proportionally thinner walls than arteries but proportionally larger lumen size to arteries, it returns blood to the heart, and contains a large percentage of the total blood volume. Contains valves to help return the blood to the heart

Four chambers of the heart

Right atrium, right ventricle, left atrium, left ventricle

Tricuspid/right atrioventricular valve

Between the right atrium and ventricle

Pulmonary valve

Between the right ventricle and the pulmonary artery

Mitral/ bicuspid/ left atrioventricular valve

Between the left atrium and ventricle

Aortic valve

Between the left ventricle and aorta

Superior/inferior vena cava

Carry deoxygenated blood back to the heart, enters via right atrium

Left/right pulmonary artery

Carries deoxygenated blood from the heart to the lungs, left and right branches, exits the heart via the right ventricle

Left/right pulmonary veins

Carry oxygenated blood from lungs back to heart enters via left atrium

Aorta

Main artery of the body, supplies oxygenated blood to the bodies tissues, exits vis left ventricle.

Coronary arteries

delivery of oxygenated blood to cardiac muscle of heart. The heat does not use the blood flowing in its chambers

Steps of blood flow

1.      Deoxygenated blood enters he heart via superior and inferior vena cava

2.      Deoxygenated blood then travels into the right atrium, then right ventricle

3.      Then the deoxygenated blood leaves the heart and enters the pulmonary circulation via the pulmonary arteries 

4.      Deoxygenated blood enters the lungs for oxygenation (pulmonary circulation)

5.      Oxygenated blood then travels back to the heart and enters vis pulmonary veins

6.      Oxygenated blood then enters the left atrium and then left ventricle

Oxygenated blood travels out into systemic circulation vis aorta

Systemic circulation

Distribution of oxygenated blood from the heart to the blood tissues via the systemic arteries, arterioles, and capillaries, the venous return of deoxygenated blood to the heart via systemic veins, venules, and capillaries

Pulmonary circulation

Movement of deoxygenated blood from heart through lungs via pulmonary arteries and capillaries. The venous return of the oxygenated blood to the heart via pulmonary venules and veins

The structure of the heart inside out

1.      Endocardium:  endothelium and connective tissue that lines the valves and chambers

2.      Myocardium: cardiac muscle that forms the bulk of the heart wall

3.      Epicardium: a visceral layer of serous pericardium

4.      Pericardial cavity: fluid-filled to allow friction-free movement

5.      Pericardium: parietal layer of serous pericardium, superficial layer of fibrous pericardium that protects and anchors the heart to the diaphragm

Conduction pathway

Cells of the SA node are autorthymic, they spontanously depolarise (give rise to an action potential). The action potential then travels along causing a contraction, both artia then both ventricles contract

The pathway of a conducting system

Sinoatrial node (SA), Atrioventricular (AV) node, Atrioventricular bundle (bundle of HIS), Left/right bundle branches, Purkinje fibers

1. Sinoatrial node (SA)

the origin of every heartbeat, located at the right atrial wall, the SA node spontaneously and repeatedly depolarises approximately 75 times/min, the SA node acts as a pacemaker and sets the rhythm of the electrical excitation, causing the contraction.

Pacemaker potential:

Auto-rthymic cells do not have a stable resting membrane potential instead, there is a positive increase in voltage between the end of an action and the start of the next one

2. Atrioventricular (AV) node:

located at the base of the right atrium, at AV node, the action potential slows, allowing both atria to empty their blood into the ventricles

3. Atrioventricular bundle (bundle of HIS):

originates at the AV node and enters the interventricular septum, the only electrical connection between atria and ventricles, carries the action potential from the AV node to the bundle branches

4.   Left/right bundle branches:

action potential enters both right and left bundle branches, which extends through the interventricular septum towards the apex of the heart

5. Purkinje fibers:

conduct action potential, beginning at the apex of the heart upwards to the remainder of the ventricular myocardium

Blood pressure

The amount of pressure exerted on the vessel’s wall by the blood

Systolic pressure

The highest pressure within the arteries during ventricular emptying, contraction of the ventricles

Diastolic pressure

The lowest pressure within arteries during ventricular filling, relaxation of the ventricles

Stroke volume (SV)

Amount of blood out of the ventricles SV=EDV-ESV                                                                    

End diastolic volume (EDV)

Volume at the end of the relaxation portion

End systolic volume (ESV)

Amount of blood left inside after contraction

Cardiac output (CO)

The amount of blood circulating through the blood vessels in 1 min CO=SVxheart rate

Mean arterial pressure (MAP)

The mean pressure being exerted by the arteries

MAP= diastolic BP+1/3(systolic pressure-diastolic pressure)

Ejection fraction (EF)

Is the percentage of blood pumped out of the heart's left ventricle with each heartbeat.

Factors influenceing (MAP): vascular resistance:

the amount of resistance to blood flow in the blood vessels caused by friction between th blood and the vessel wall, depending on the size of vessel lumen (diametre decreases = resistance increases), blood viscosity (blood viscocity increases = resistance increases), blood vessel length (length increases= resistance increases)

Factors influenceing (MAP): cardiac output:

   Driven by stroke volume and heart rate if stroke volume increases and heart rate increase the CO will also increase. If the stroke volume and heart rate decrease then the CO will also decrease.

 

Importance of regulating MAP

excess high blood pressure can damage blood vesseles and surrounding tissues and low pressure can result in poor blood perfusion, leaving tissue starved for oxygen and nutrients

Negative feedback loop that regulates blood pressure:    

Stimulus- disruption of the normal BP range                                                                                              receptor- pressure sensitive nerve endings (mechanoreceptors) in the blood vessel walls that detect the change                                                                                         control centre: brain processes info on the change of BP effectors: autonomic nervous system/heart and blood vessels directed to respond                                                      response: BP restored to normal ranges                                                                    

Baroreceptors

Baroreceptors monitor the pressure of blood flowing to the brain (carotid baroreceptor) and the body (aortic baroreptors)

Firing rates of baroceptors (nerve impulses) are proportional to BP. As BP increases, the firing rate also increases; as BP decreases, the firing rate also decreases

Cardiovascular centre is in the medulla oblongata

Functions of the lymphatic system

Drainage of excess interstitial fluid, transports lipid and lipid-soluble vitamins from the gastrointestinal system into the blood, carries out immune responses, directed against  foreign cells, transports immune cells and antigens to lymph nodes to be checked or/and destroyed.

Components of the lymphatic system

Lymphatic fluid- clear fluid, from blood plasma, moves from the interstitial space between body tissue into lymphatic vessels

lymphatic vessels

lymphatic organs/tissues lymph nodes- composed of a type of connective tissue that contains a large number of lymphocytes

Primary lymphatic organs

The site where stem cells divide and become capable of mounting an immune response

Secondary lymphatic organs/tissues

The site where most immune responses occur, lymph nodes, spleen, lymphatic nodules

Lymph nodes

Small bean-shaped composed of connective tissue, approximately 600 in the body, located mostly around the lymphatic vessels. Lymph enters through afferent vessels, passes through the node, and leaves via efferent vessels. Lymph nodes function by trapping foreign substances in the node

Lymph vessels

begin as lymphatic capillaries that are closed on one end, they have a greater permeability than blood permeability, thus they can absorb larger molecules such as lipids and proteins. Many lymphatic capillaries form larger lymphatic vessels that resemble veins in structure but with thinner walls and more valves. Lymphatic vessels will then converge into lymphatic trunks and then into ducts before draining into the venous blood  

Lymphactic circulation sequence

Blood capillaries (blood)

interstitial spaces (interstitial fluid)

lymphatic capillaries (lymph)

lymphatic vessels (lymph)

lymphatic trunks and ducts (lymph)

venous return to the heart (blood)

Maintenance of lymph flow: Skeletal muscle pump

   The contraction causes compressions of lymphatic vessels, propelling the lymph upwards. Valves within the lymphatic vessels function by stopping lymph backflow

Maintenance of lymph flow: Respiratory pump

  Lymph flow is driven by the pressure changes that occur during inhalation. When pressure in the thoracic cavity decreases, lymph flows in from higher pressure eg. the Abdominal region, to follow the concentration gradient.