Circulatory system Flashcards
Describe the heart and position
The Heart•Hollow coned shaped muscular organ -approximately size of the owners fist•It lies in the thoracic cavity, obliquely in the mediastinum, behind the sternum.•2/3 lies to the left of the midline,•Base above, apex below, resting on the diaphragm.
Three layers of the walls of The Heart
Three layers of the walls of The Heart •Pericardium – fibrous outer sac –2 layers •Myocardium – muscle layer, thickest in the left ventricle, has its own intrinsic stimulus, coronary arteries found here •Endocardium – smooth inner lining continuous with blood vessels
Pericardium
Pericardium•Consists of two sacs–an outer fibrous sac (Fibrous pericardium)–a double inner layer of serous membrane •The outer layer of serous membrane, called the parietal pericardium adheres to the outer fibrous pericardium•The innermost layer of serous membrane, called the visceral pericardium adheres to the myocardium
Myocardium
MyocardiumIs the muscle layer of the heart. It is thickest around the left ventricle and has a unique characteristic, called Automaticity.This means the heart can contract without an outside stimulus
Endocardium
EndocardiumThe innermost lining of the heart and its valves, it is composed of endothelium, providing a smooth lining and preventing local blood clotting
Three main components of the circulatory system + what
Three Main Components •
The heart •
Blood vessels •
Blood
and control mechanisms
Heart chambers
Heart ChambersFour chambers •Left and right atria •Left and right ventricles •Left and Right sides are divided by muscular partition called the septum
Heart valves
Heart ValvesFour valves: •Pulmonary valve •Aortic valve •Two atrioventricular valves–Right or tricuspid valve–Left or mitral valve
Pulmonary & Systemic circulation
Pulmonary & Systemic Circulation •Pulmonary – involves pumping deoxygenated blood to the lungs and returning re-oxygenated blood to the heart •Systemic – involves circulating oxygenated blood throughout the body to the tissues and returning deoxygenated blood to the heart
Types of blood Vessel
The heart pumps blood into vessels that vary in structure, size, and function, and there are several types:• arteries• arterioles• capillaries• venules• veins
Structure of Blood Vessels
Structure of Blood Vessels
All vessels are structured in three layers: •
Tunica Adventicia (Outer fibrous sheath) •
Tunica Media (middle layer of muscle and elastic tissue)
•Tunica Intima (Inner layer of smooth endothelium)
Portal circulation
Portal Circulation•A branch of the systemic circulation•Carries blood to and from the liver•Hepatic artery supplies oxygenated blood•Hepatic portal vein carries blood rich in nutrients from the digestive tract to the liver•Hepatic Veins carry deoxygenated blood from Liver to Inferior Vena Cava
Spleen
Spleen•Lies in the left hypochondrial region of the abdominal cavity, between fundus of the stomach and the diaphragm •Size varies but usually approx. 12cm long, 7cm wide and 2.5cm thick •Weighs approx. 200g
Function of the spleen
Functions of the Spleen •Produce new white blood cells •Store red blood cells •Destroy old red blood cells
Composition of blood
Composition of Blood Blood is composed of 55% liquid, 45% solids and contains four main elements: •Plasma (Liquid) •Red cells (erythrocytes) •White cells (leukocytes) •Platelets (thrombocytes)
Principle functions of blood
Principle Functions of Blood•Carry oxygen and carbon dioxide•Carry nutrients and water •Carry waste products to excretory organs •Distribute secretion of glands (Enzymes and hormones) Protect the body from infection •Distribute heat •Seal wounds by clotting
Plasma
Plasma
Plasma is a straw coloured transparent fluid made up of approximately 90% water and 10% dissolved substances like proteins, mineral salts, and nutrients like fats and carbohydrates .
It is responsibile for carrying the solid constituents of blood around the body in order for them to carry out their specific function.
Red blood cells (erythrocytes)
Red blood cells (erythrocytes)
Red blood cells are bi-concave discs. There are approximately 5.5 million per cubic millimetre of blood and they are produced within the red bone marrow of some bones.
They contain a protein called haemoglobin, made up of two substances, globin and haem. Haem is an iron containing pigment that gives the cell its colour, globin is a protein.
Haemoglobin has a great affinity for oxygen, and this helps to carry the gas around the body. In an oxygen-enriched state it is called oxyhaemoglobin.
When the oxygen is given up at the tissue level, the haemoglobin attracts carbon dioxide from the tissues and then carries it back to the lungs for exhalation from the body. Haemoglobin in this state is called carbaminohaemoglobin.
Red blood cells have a life span of approximately 120 days, after which they are destroyed by the spleen or liver.
White blood cells (leukocytes)
White blood cells (leukocytes)
These cells are larger than red blood cells and consequently there are less of them - approximately 9,000 per cubic millimetre of blood.
It is possible to divide this group of cells into five sub groups, but for the purpose of this course we will treat them all as one.
White cells as a whole have two major functions:
To fight infection
To provide the body with immunity
Platelets (thrombocytes)
Platelets (thrombocytes)
Platelets are small colourless bodies that react with enzymes, proteins and mineral salts when an injury occurs to form a blood clot, thus preventing the escape of too much blood.
This process can be faulty in some illnesses such as haemophilia
What are blood vessels?
What are blood vessels?
Blood is transported around the body in tube-like vessels. There are several different types of blood vessel and they differ in structure according to location and function.
Arteries carry blood away from the heart. As these arteries become smaller they are called arterioles. In turn, as arterioles become smaller they become capillaries. Capillaries have extremely thin walls through which the oxygen and nutrients are delivered to the tissues.
The walls of the capillaries only allow certain size molecules to pass through, this is why blood plasma and other blood cells (large molecules) remain within the circulation while oxygen and nutrients move on to the tissues.
Waste products of tissue metabolism are returned to the capillaries and on, back to the heart. The return journey is via the venous system. Capillaries begin to get larger and their walls thicker at which stage they are called venules. They continue to enlarge and become known as veins. Veins always carry blood back to the heart.
In order to aid the return of blood to the heart, some veins, especially those of the lower extremities and the arms, possess tiny valves that prevent backflow and maintain the forward momentum of the blood returning to the heart.
What is the capillary network?
What is the capillary network?
Capillaries surround and penetrate whatever tissue or organ they are supplying, forming what is termed a capillary network or bed. The exchange of gases and nutrients for waste products takes place within and through this network.
The smooth muscle within the construction of the arterioles and venules is responsible for maintaining the correct blood pressure within the capillary network.
Systemic circulation
Systemic circulation
Systemic circulation is made up of those vessels that supply the major organs and systems of the body and emanate from the left ventricle of the heart, via the aorta , and drain back into the right atrium of the heart via the superior and inferior vena cava .
Pulmonary circulation
Pulmonary circulation
Pulmonary circulation is made up of those vessels that take deoxygenated blood from the right ventricle of the heart, via the pulmonary artery to the lungs, and oxygenated blood from the lungs, via the pulmonary veins back to the left atrium of the heart