Cardiovascular system overview

the cardiovascular system is composed of 3 components

• blood

• heart

• vascular system (blood vessels)

cardiovascular system functions

• regulation of body temp

• fluid homeostasis

• control of O2 and nutrient supply

the heart is 2…

electrically driven pumps connected in a series

blood is moved by two pumps: the ___ and the ___

heart, blood vessels

blood vessels are an extensive system of

thin vessels called capillaries that permit rapid exchange between tissues and the vascular channel

single cells do not need a ___ system, instead they achieve metabolic homeostasis by

circulatory; diffusion and convection of solutes from external to internal milleu

why is the circulatory system needed for humans?

we are large and complex multicellular organisms; diffusion is not enough because the distance between the external environment and our cells is too long

unicellular organisms participate in ___ transport

diffusion and other membrane-bound

multicellular organisms participate in ___ transport

bulk

functions of blood

• deliver O2 and nutrients

• transport waste products and CO2

• transport hormones

• maintain body temp, pH, and fluid volume

• prevent blood loss and infection

total blood volume in adults

men: 75 ml/kg

women: 65 ml/kg

blood is made up of

plasma and cells

plasma is made up of

• water

• electrolytes

• plasma proteins

• carbs

• lipids

plasma proteins are classified into two main categories

albumin + globulins

in adults, plasma is what % of blood volume?

50-55%

cells make up what % of blood volume?

45-50%

water makes up what % of plasma volume

90%

the concentration of the different components of plasma is influenced by

diet, metabolic demands, hormones, vitamins

plasma proteins is what % of plasma weight

7%

most plasma proteins except for antibodies are produced by

the liver

the cellular component of blood are 3 types of cells

erythrocytes, leukocytes, platelets

all blood cells originate from

stems cells in the bone marrow

all blood cells are divided into 2 lineages which give rise to

lymphoid = leukocytes

myeloid = all other blood cell types

myeloid lineage gives rise to what cells

erythrocytes, monocytes, eosinophils, neutrophils, and platelets

lymphoid lineage gives rise to what cells

B and T lymphocytes, natural killer cells

erythrocytes make up ___ % of blood in men and ___ % of blood in women

48%; 42%

what happens when you spin a tube of blood down?

erythrocyte cells sink to the bottom, leukocytes and platelets form the buffy coat on top of the cells, and the plasma floats on top

hematocrit is the fraction of…

fraction of the blood column in a tube sample that is occupied by erythrocytes; ratio of RBC’s in your blood

structure of erythrocytes

• no nucleus

• biconcave

• flexible

why are erythrocytes shaped the way they are? (biconcave and flexible)

so that they can maximize their surface area for maximum diffusion and minimize intracellular diffusion differences for gas exchange

function of myeloid cells

recognize bacteria and pathogens and destroy them

which myeloid cell is the most abundant?

neutrophils

neutrophils function

destroy bacteria and fungi by release of microbicidal molecules and phagocytosis

monocytes function

develop into macrophages to clear bacteria or damaged cells by phagocytosis

eosinophils function

turn off allergic response and kill parasites

basophils function

release histamine and other mediators of inflammation

T cells function

kill infected cells, activate other immune cells, and produce cytokines that regulate immune response

B cells function

produce antibodies

how to platelets originate?

myeloid stem cell differentiates into a megakaryoblast, then to a megakaryocyte, then produce platelets

what are platelets?

cellular fragments that originate from megakaryocytes

each megakaryocyte gives rise to a few ___ platelets

thousand

normal blood contains ___ to ___ of platelets

150,000-450,000

thrombocytopenia is ___ and increases the risk of what?

too few platelets; increases risk of abnormal bleeding

thrombocytosis is ___ and increases the risk of what?

too many platelets; increases risk of abnormal clotting

hemostasis is achieved by 4 methods

• vasoconstriction

• increased tissue pressure

• platelet plug formation

• clot formation

hemostasis balances which two pathways?

anticoagulant and procoagulant

procoagulant forces

• platelet adhesion and aggregation

• fibrin clot formation

anticoagulant forces

natural inhibitors of coagulation and fibrinolysis

once the bleeding stops, damaged blood vessels are ___ to restore normal blood flow

remodeled

primary hemostasis accomplishes ____

formation of platelet plugs

how does primary hemostasis form platelet plugs?

plug small holes in vascular endothelium via adhesion, activation, aggregation

secondary hemostasis accomplishes

deposition of fibrin

secondary hemostasis deposit fibrin through which two pathways

intrinsic and extrinsic pathway

primary hemostasis steps

• initial injury causes vasoconstriction to stop blood loss

• vessel injury sends humoral signals that allows surface platelet receptors to bind to ligands around tissue damage (adhesion)

• binding triggers platelet activation and cytoplasmic granules secrete their contents which recruits and activates more platelets

• platelets aggregate and form a mass that covers the endothelial injury

a blood clot is a semisolid mass of …

serum, platelets, erythrocytes, and leukocytes in a mesh of fibrin

a thrombus is a …

blood clot inside a blood vessel

platelet plug formation and blood clotting may occur in ___ or in ___

alone; parallel

intrinsic pathway of clot formation starts when

blood contacts a negatively charged surface

the extrinsic pathway of clot formation starts when

blood contacts damaged cell membranes

in clot formation of both pathways, the trigger event causes a chain reaction:

• inactive clotting factors are converted into activated factors

• both pathways converge onto a common pathway that generates thrombin and stable fibrin

the clotting pathway is a (positive/negative) feedback loop

positive feedback via thrombin; deposition of fibrin drives clot formation

both the intrinsic and extrinsic pathways form factor ___

factor XA

thrombosis is …

thrombus formation

embolus is …

a thrombus traveling through the circulation

what mechanism prevents clotting under normal circumstances and why?

antithrombotic mechanisms; limits clotting to the sites of vascular injury

antithrombotic mechanisms occur via ___ and ___

antithrombin factors and fibrinolytic systems

endothelial cells produce what molecules to inhibit plate binding, secretion, and aggregation?

prostacyclin and nitric oxide

what cells produce antithrombin and what is its function

produced by endothelial cells; stops the positive feedback loop due to thrombin

fibrinolytic mechanisms

endothelial cells produce tissue-type and urokinase-type plasminogen activators that converts plasminogen to plasmin to break down fibrin

which plasminogen activator is used in people with strokes to break up clots?

u-PA: urokinase plasminogen activator

the right heart is a ___ pump to the ___ circulation

low-pressure; pulmonary

the left heart is a ___ pump to the ___ circulation

high-pressure; systemic

the right ventricular wall is ___ mm thick whereas the left ventricular wall is ___ thick because..

4-5 mm; 12-15 mm; the left side of the heart pumps blood at a higher pressure

blood flow pathway to the lungs

RA - RV - R/L pulmonary artery

oxygenated blood flow pathway into circulation

LA - LV - out in aorta

atria are (low/high) pressure producing chambers

low

right atrium receives blood from which circulation?

systemic; deoxygenated

left atrium receives blood from which circulation?

pulmonary; oxygenated

pulmonary circulation is responsible for ___-pressure blood flow to the lungs

low-pressure

• thin RIGHT ventricular walls

systemic circulation is responsible for ___-pressure blood flow to the rest of the body

high-pressure

• thick LEFT ventricular walls

blood flow in L/min is the ___ in both circulations

same

the aortic and pulmonary valves are between

the ventricles and the aorta and pulmonary artery

AV valve attachments

upper ends attach to one of the rings in the fibrous cardiac skeleton

lower ends attach to papillary muscles

papillary muscles

extensions of cardiac muscle that hold the AV valve cusps in place during ventricular contraction to prevent prolapse into the atria

the (left/right) AV valve is called ___ because it has ___ cusps

right; tricuspid; 3 cusps

the (right/left) AV valve is called ___ and has ___ cusps

left; mitral valve; 2 cusps

the pulmonic and aortic valves are also knowns as the ___ valves and have ___ cusps

semilunar; 3 cusps

the four heart valves open and close due to

pressure gradients between the atria and ventricles and between the ventricles and arteries

what happens during ventricular relaxation?

the AV valves open and blood flows from the higher pressure in the atria to the lower pressure in the ventricles

what happens when ventricular pressure increases?

the AV valves close and the semilunar valves of the heart open when the ventricular pressure exceeds aortic and pulmonary pressure

what happens when ventricular contraction ends?

ventricular pressure drops, pulmonary and aortic valves close when vascular pressure is greater than ventricular pressure

• prevents backflow

the first heart sound is produced when

the AV valves close

the second heart sound is produced when

the semilunar valves close

3 layers of the heart wall

epicardium, myocardium, endocardium

the heart is enclosed in a double-walled membranous sac called

the pericardium

pericardial sac functions

• prevents displacement of the heart during acceleration and deceleration

• physical barrier that protects the heart from infection/inflammation

• contains pain receptors and mechanoreceptors

epicardium

outer layer of the heart; smooth surface allows cardiac movement with the pericardium

myocardium

thickest layer; composed of cardiac muscle anchored to the heart’s fibrous skeleton

endocardium

lines the inside of the atrium and ventricles; composed of connective tissue and a layer of squamous epithelial cells (endothelial cells)

a large portion of coronary arteries pass through

the fat layer in the heart