Physiology 1 - Cardiovascular Overview Pp

7/31/2019 Physiology 1 - Cardiovascular Overview Pp

1/41

Cardiovascular systemoverview

Randa MostafaRanda MostafaHead, Basic Medical Sciences Department

Prof of Medical PhysiologyExt. 7204

E mail:[email protected]


2/41

Profile

Silent

Feel free to make notes, but donttry and copy everything I show and

say you wont have time. I wouldrather that you just listen.

If you have a question please catchmy attention I am more than happyto stop.

The recommended coursetextbooks cover my lectures well.

If you need a copy of thispresentation, then you can get itfrom the black board.


3/41


4/41

MAIN FUNCTIONS OF THEMAIN FUNCTIONS OF THE

CIRCULATORY SYSTEMCIRCULATORY SYSTEM

Transport and distribute essential

substances to the tissues.

Remove metabolic byproducts.

Adjustment of oxygen and nutrient supply

in different physiologic states.

Regulation of body temperature.


5/41

The system has two major

divisions:

:

which carried blood to thelungs for gas exchange and

returns it to the heart.

:

which supplies blood toevery organ of the body.


6/41

The right

side of the

heart servesthe

pulmonary

circuit

The left sideThe left side

serves theserves the

systemicsystemiccircuit.circuit.


7/41

has a tough, superficial fibrous layerof dense

irregular connective tissue and a deep, thin

serous layer.

The heart is enclosed in a

double-walled sac called the

The outer wall,called the

(pericardial sac).

The serous layer turns inward at the base of the

heart and forms the (epicardium)

covering the heart surface .


8/41

The pericardial sac is anchored by ligaments to the

diaphragm below and the sternum anterior to it.

Between the parietal and visceral membranesBetween the parietal and visceral membranes

is a space called theis a space called the ..

ItIt

contains 5 to 30contains 5 to 30 mLmL ofof

The pericardiumThe pericardium


9/41

The pericardial fluidlubricates the membranes

and allows the heart to

beat almost without

friction.

: Pericardialdisease manifest itself by the

accumulation of fluid in the

pericardial space (pericardial

effusion) and /or inflammation

of the pericardium (pericarditis).

The pericardial cavity can fill with up to2 litters of serous fluid(hydropericardiumhydropericardium )) or blood

((hemopericardiumhemopericardium)) that preventnormal diastolic filling and therebyreduces cardiac output.


10/41

PUMP

DISTRIBUTING

TUBULESTHIN

VESSELS

COLLECTING

TUBULES

THE MAIN CIRCUIT


11/41

There are 3 primary blood vesselThere are 3 primary blood vessel

types:types:

1.1. ArteriesArteries : which carry blood

away from the heart.

2.2. VeinsVeins : which carry bloodtowards the heart.

3.3. Capillaries :Capillaries : tiny blood

vessels that function in the

exchange of gases, nutrients,

and wastes between the blood

and the interstitial fluid.


12/41

The walls of both arteries and veins have 3The walls of both arteries and veins have 3

layers that surround the lumen:layers that surround the lumen:1. Tunica externa

Outermost layer. Made primarily of looseconnective tissue. Anchors the bloodvessel to the surrounding tissue.

2. Tunica MediaConsists primarily of smooth muscle andis responsible for vasoconstriction and

vasodilatation. Usually the thickest layerin arteries.

3. Tunica Interna (Endothelium) Acts as a

selectively permeableselectively permeable barrier to bloodsolutes.

Secretes vasoconstrictors andSecretes vasoconstrictors and

vasodilators.vasodilators.

Provides a smooth surfaceProvides a smooth surface that repelsblood cells and platelets.


13/41

They are constructed to withstandThey are constructed to withstand

surges of blood pressure associated withsurges of blood pressure associated with

ventricular systoleventricular systole..

They're more muscular than veins and appearThey're more muscular than veins and appear

relatively round in tissue sections.relatively round in tissue sections.

They retain their round shape even when empty.They retain their round shape even when empty.

There are 3 basic categories of arteriesThere are 3 basic categories of arteries


14/41

Conducting (or Elastic) Arteries

Distributing (or Muscular) Arteries

Arterioles


15/41

1. Conducting (or Elastic) Arteries

The largestThe largest

oExamples include the aorta, pulmonary arteries,and the common carotid arteries.


16/41

Their tunica media contains agreat deal ofelastic tissue.

The elastic tissue allows for

expansion during ventricular

systole and recoil during

ventricular diastole.

This helps create continuous

flow from a discontinuous

pump.


17/41

Conducting arteries expand during ventricular systole toConducting arteries expand during ventricular systole to

receive blood, and recoil during diastole:receive blood, and recoil during diastole:

*Their expansion takes some of the pressure off the blood so thatsmaller arteries downstream are subjected to less systolic stress .

* Their recoil between heart beats prevents t he blood

pressure from dropping too low while the heart is relaxingand refilling.

Lessen the fluctuations in blood pressureLessen the fluctuations in blood pressure


18/41

2. Distributing (or Muscular) Arteries

* Smaller branches ,distribute blood to individual organs.

*They have 25-40 layers ofsmooth muscle cellssmooth muscle cells

constituting about three quarters of the wall thickness.

* Examples include the brachial, femoral, and splenic arteries


19/41

3. Arterioles

Smallest of the three.

They are heavily innervated .

The primary points at which the body controls the

relative amounts of blood directed to specific organs.


20/41

Linking the arterioles

to the capillaries areshort vessels known

as

Part of their wall surrounded

by smooth muscle

These muscle cells form whichencircle the entrance to a capillary bed.


21/41


22/41

Certain major arteries above

the heart have sensorystructures in their walls that

monitor blood pressure and

chemistry.

They transmit information to

the brain stem that is used to

regulate the heart beat,

vasomotion and respiration.


23/41

The sensory receptors are of three kindsThe sensory receptors are of three kinds

1. Carotid sinuses. These arebaroreceptorsbaroreceptors (pressure sensors) that

respond to changes in blood pressure.

* Thin tunica media

* An abundance of glossopharyngeal

nerve fibers in the tunica externa.stretches th

thin media and stimulates the nerve

fibers which transmits signals to thevasomotor and cardiac centers of the

brainstem, which responds by lowerin

the heart rate and dilating the bloodvessels, thereby lowering the blood

pressure.

The carotid sinuses

are located in the

wall of the internal

carotid artery


24/41

2. Carotid bodies: located near

the branch of the commoncarotid arteries.

They primarily transmitThey primarily transmit

signals to the brainstemsignals to the brainstem

respiratory centers, whichrespiratory centers, which

adjust breathing to stabilizeadjust breathing to stabilizethe blood pH and its COthe blood pH and its CO22 andand

OO22 levelslevels


25/41

Aortic bodies:Aortic bodies: These are one

to three chemoreceptors

located in the aorticarchThey are structurally similar tothe carotid bodies and have

the same function.


26/41

CapillariesCapillariesThere are approximately 1 billion of them in the human body.

Capillaries are organized into groups of 10-100 in capillary beds

There are 3 separate types of capillaries:

1. Continuous Capillaries

3. Sinusoidal Capillaries


27/41

1. Continuous Capillaries

Endothelial cells are joined by tight junctions.but contain intercellular clefts through which small molecules

(e.g., glucose, but not albumin) can pass.

Most common.Most common.

Abundant in skin and muscleAbundant in skin and muscle.

Cerebral capillariesCerebral capillaries lack these clefts and have far more

numerous tight junctions forming the blood brain barrier which

helps protect the delicate brain tissue from blood-borne toxinsand pathogens.


28/41

Some continues capillaries

exhibit cells called pericytespericytes

that lie external to the

endothelium

Pericytes are contractilecontractile,,

have elongated tendrils that

wrap around the capillary

It thought that they contract and regulate blood flowIt thought that they contract and regulate blood flow

through the capillaries.through the capillaries.

They also can differentiate into endothelial and smoothThey also can differentiate into endothelial and smooth

muscle cells and thus contribute to vessel growth andmuscle cells and thus contribute to vessel growth andrepair.repair.


29/41

2. Fenestrated capillaries2. Fenestrated capillaries

Similar toSimilar tocontinuouscontinuous

capillaries butcapillaries but

some of thesome of theendothelial cellsendothelial cells

has filtration poreshas filtration pores

fenestrationsfenestrations..

These pores allow forThese pores allow for

the rapid passage ofthe rapid passage ofmolecules, evenmolecules, even

proteins , through theproteins , through the

capillary wall.capillary wall.

Found in sites of activeFound in sites of active

absorption (small intestine),absorption (small intestine),

secretion (endocrinesecretion (endocrine

organs) and capillaryorgans) and capillary

filtration (kidneys).filtration (kidneys).


30/41

3. Sinusoidal Capillaries

Highly modified, extremelyleaky, fenestrated capillaries

Found in locales where large stuff needsFound in locales where large stuff needs

to exit/enter the bloodstreamto exit/enter the bloodstream.

Such sites include bone marrowbone marrow (for

passage of nascent blood cells), lymphoidlymphoidorgansorgans (for easy entry/exit by WBCs) and

the liverthe liver (for large plasma proteins, e.g.,

albumin).

Contain irregularly shaped lumen and large intercellular cleftsContain irregularly shaped lumen and large intercellular clefts


31/41

In the liver and the spleen , the

endothelium is intimately

associated with macrophages.macrophages.

In these locations the sinusoidsare twisty and tortuous,

conformed to the shape of the

surrounding tissue. . TheThetwistinesstwistiness makes blood flowmakes blood flow

extra slowly which gives timeextra slowly which gives time

forfor splenicsplenic and hepaticand hepatic

macrophages to monitor andmacrophages to monitor and

assess its contentsassess its contents..


32/41

Just by looking at this image, can you identify theJust by looking at this image, can you identify the

different capillary types?different capillary types?


33/41

VeinsVeinsThecapacitance vessels of the cardiovascular system

because :

They are relatively thin-walled and flaccid.

Expand easily to accommodate an

increased volume of blood.

At rest, about 54% ofAt rest, about 54% of

the blood is found inthe blood is found in

the systemic veins asthe systemic veins as

compared with onlycompared with only11% in the systemic11% in the systemic

arteriesarteries


34/41

Being distant from the ventricles of the heart,

they are subjected to relatively low blood

pressure.

In large arteries, blood pressure averages 90 to

100 mm Hg (millimeters of mercury) andsurges to 120 mm Hg during systole, whereas

in veins it averages about 10 mm Hg.

Considering the relatively low pressure inConsidering the relatively low pressure in

the veins.the veins.

how blood is forced through them to get back to thehow blood is forced through them to get back to theheart????heart????


35/41

It's a combination of 3 separate thingsIt's a combination of 3 separate things:

1.Skeletal Muscle Pump .

2. Respiratory Pump .

3. Venous Valves


36/41

1.1. Skeletal MuscleSkeletal Muscle

PumpPump :- the

contraction/relaxation

cycles of skeletal

muscles squeeze the

veins forcing thecontained blood

towards the heart.

It's a combination of 3 separate

things:

1.Skeletal Muscle Pump .2. Respiratory Pump .3. Venous Valves


37/41

2. Respiratory Pump2. Respiratory Pump : as we inhale,

our thoracic cavity expands while

our abdominal cavity compresses.

pressure within veins of the

thoracic cavity drops.

Meanwhile, pressure in theabdominal veins increases.

This combination results inincreased blood flow towards that

heart.


38/41

3. Venous Valves:3. Venous Valves: - one-way

valves (similar to the

semilunars of the heart) madeof flaps of endothelium are

found in medium veins

(mostly in the legs and the

arms) where they help prevent

backflow.


39/41

:In people who stand for long

periods, blood tends to pool in the

lower limbs and stretch the veins.This is especially true of superficial

veins, which are not surrounded by

supportive tissue.

Stretching pulls the cusps of the

venous valves farther apart until the

valves become incompetent toprevent the backflow of blood


40/41

As the veins become furtherAs the veins become further

distended, their walls growdistended, their walls growweak and they develop intoweak and they develop into

varicose veinsvaricose veins with irregularwith irregular

dilations and twisted pathways.dilations and twisted pathways.


41/41

Physiology 1 - Cardiovascular Overview Pp

Documents

Transcript of Physiology 1 - Cardiovascular Overview Pp