Cardiovascular 1B Heart and Circulation, Location of Heart, Role in the Circulatory System

Cardiovascular 1b – Heart and Circulation, Location of Heart, Role in the Circulatory System

Anil Chopra

The human heart beats continuously throughout life, over 2½ billion times.
Movement is dependent of contraction and four valves (tricuspid, mitral, pulmonary and aortic)
An average adult contains 5l of blood in the body, and heart pumps about 5l per minute.

1. Location of heart within chest

It is in the middle of the inferior mediastinum (just left of the midline)
2nd-6th costal cartilage
The left edge (apex) extends to the mid-clavicular line.
The pericardial cavity is between the lungs and above the diaphragm.
The left side of the heart pushes the lung and pleura over and this region is known as the cardiac notch.
Borders of heart
Anterior right edge RIGHT ATRIUM
Anterior inferior edge RIGHT VENTRICLE
Anterior superior left edge LEFT VENTRICLE
Posterior edgeLEFT ATRIUM (oesophagus)

The heart is enclosed by pericardium

Tough fibrous sac with serosal lining.
Parietal layer and inner serosal layer.
Fluid in pericardial cavity between the two surfaces allows movement of the heart. Made from mesothelial cells with rich fibroconnective tissue – rich in blood supply.
Visceral layer – serous pericardium
Muscle layer – myocardium
Inner layer – endocardium (continuous with lining of blood vessels)

Cardiac Muscle

Made from quadrangle cells joined on end (syncitium)
ANASTOMOSIS of fibres (joining branch diversions)
No sarcolemma exists.
Clear oval nuclei.

Surface Grooves

Atrioventricular groove – separates atria and ventricles and contains the coronary sinus.
Inner atrial groove – separates 2 atria (not seen on anterior because arteries cover it)
Anterior longitudinal sulcus – sternocostal separation of ventricles.
Posterior longitudinal sulcus – diaphragmatic separation of ventricles.

2. Major vessels returning blood to heart

Vena Cava- Split into inferior and superior

-Superior is smaller and comes from upper part of the body, it has no valve.

-Inferior is larger and comes from lower half of the body. Has rudimentary value.

Coronary - Returns blood from heart muscle

Sinus- Goes to right atria

-Has a semicircular valve.

-Foramina venarum minimarum has similar function.

Pulmonary - 4 of them return oxygenated blood to the left atrium.

Veins- Have no valves.

3. Major vessel bringing blood to lungs

Pulmonary - Circular opening near ventricular septum.

Artery- Comes from right ventricle

- Guarded by pulmonary semi-lunar valves.

4. Major vessel bringing oxygenated blood to body

Aorta- Comes from left ventricle.

-Guarded by aortic semilunar valves.

-Aortic vestibule below aortic opening.

-Wall is fibrous instead of muscle.

5. Define artery, vein, arteriole, venule, capillary

In adults blood vessels are 100 000 miles long!

Artery

passes blood from heart to organs

high pressure (110-150/60-80)

main aorta branches out into arteries

Vein

Passes blood from organs to heart.

All (apart from pulmonary vein) carry deoxygenated blood.

Thin walled.

Have valves formed by reduplication of lining membrane which prevent the backflow of blood.

Low pressure.

Arteriole

Smaller arterial branches

Lead into capillaries

A resistance vessel

Venules

Small tributaries of veins

 Arise from capillaries

Capacitance vessels

Capillaries

Thin walled blood vessels in which gas exchange occurs.

Concentrated in capillary beds

Some have small pores in walls to allow movement of fluid,

Nutrients, wastes and hormones are exchanged.

Controlled by nervous activation of sphincters.

6. What is artery made of?

Arteries are used to measure blood pressure and pulse rate. They are made up of different layers:

Artery Layers

Connective tissue

Nerve fibres

External elastic layer

Smooth muscle

Internal elastic layer

Basement membrane

Endothelium

Lumen

7. What is vein made of

Vein Layers