Cardiovascular System Flashcards
(26 cards)
What is the cardiovascular system?
Divided into 2 parts:
* Circulatory system - heart and blood vessels
* Lymphatic system - lymph nodes and lymph vessels
What are the main functions of the circulatory system?
- Transportation
- Regulation
- Protection
What is the fuction of transportation?
- Respiratory - transport O2 to the tissues and CO2 back to the lungs
- Nutritive - Absorbed digested products are transported to the liver and to the tissues
- Excretory - Waste products from metabolism are transported to the kidneys for excretion in urine
What is the function of regulation?
- Hormonal - Hormones are carried from the endocrine glands to their target tissues
- Temperature - blood can be diverted to warm or cool the body
What is the function of protection?
Clotting - Blood contains clotting factors and platelets - when activated prevent blood loss through clot formation
Immune - blood contains leucocytes, cytokines and complement which protects against infective pathogens
What are blood vessels?
- The inter-connected series of tubes which carry blood from the heart to the organs and tissues and back again
- Divided into 3 main groups
- Arteries, veins and capillaries
What are arteries?
- Transport blood away from the heart
- Have thicker walls than veins to enable them to withstand the high pressur eof arterial blood
- As they branch and become smaller they are called arterioles
What are veins?
- Return blood to the heart
- Have thinner walls because blood is under low pressure
- Some veins have valves which prevent backflow of blood ensuring it flows to the heart
- Smallest veins are called venules
What are the three layers of blood vessels?
- Tunic externa
- Tunic media
- Tunic intima
- Capillaries only have the tunica intima
What is the tunica externa?
- Connective tissue
- The outer structural wall of the vessel
- Thickest layer in veins
What is the tunica media?
- Smooth muscle
- Can be constricted to control diameter of lumen
- Thickest layer in arteries
What is the tunica intima?
- Endothelium
- Secretes vasoactive substances
- Control permeability in capillaries
What are the properties of veins?
- Veins are the main vessels which carry blood back to the heart
- Larger lumen
- Lower pressure
- Can be compressed
- Semi lunar valves to prevent backflow
- Can dilate and constrict to lesser extent to allow heat dissipation
What are varicose veins?
- If the blood stagnates in the vein and clots develops into varicose veins
- Can be surgically removed
What are capillaries?
- Form a vast network of tiny vessels which link the smallest arterioles to the smellest venules
- Small diameter
- Consist of single layer of endotherlial cells which water and small molecules can pass through
- Capillary bed is the site of exchange pf substances between the blood and tissue fluid which bathes body cells
What are the properties of capillaries?
- Link the artery to the vein
- One arteriole splits into 20-100 capillaries
- Capillaries are the smallest of blood vessels
- Only one cell thick
The heart as part of the circulatory system
The heart pumps blood into 2 separate systems of blood vessels:
* Pulmonary circulation
* Systemic circulation
Right side - blood to the lungs where gas exchange occurs (pulmonary)
Left side - blood into the systemic ciculation, supplied the rest of the body (systemic)
What is the blood flow?
- Deoxygenated blood from the body empties into the right atrium via the inferior and su[erior vena cava
- Blood passes through the tricuspid valve into the right ventricle
- From the RV the blood goes to the lungs via the pulmonary artery
- In the lungs the blood picks up oxygen and excretes CO2
- Oxygenated blood returns to the left atrium via the pulmonary veins
- Flows into the left ventricle through the mitral valve
- Left ventricle pumps blood to the body through the aorta and other arteries
What are the three layers of the heart?
Pericardium - three layers
1. Fibrous pericardium layer - surrounds and anchors the heart in place
2. Pericardium space - contains lubricant which reduces friction as heart contract and relaxes
3. Viseral layer - attached to heart surface
Myocardium (middle) - Hearts muscle acts as a pump
Endocardium (inner) - lines the chambers and forms the valves. Receives blood supply from coronary arteries
What are valves?
- Situated at the entrance and exit of ventricles
- Ensure blood moves only in one direction (forward)
- Blood flows through as a result of pressure changes
What is the Sinoatrial Node?
- Small mass of specialised cells in the wall of the right atrium
- Known as the pace-maker of the heart
- It generate an impulse which travels through the atri causing them to contract
What is thr Atrioventricular Node?
- Small mass of neuromuscular tissue in the wall of the atrial septum near the AV valves
- Responsible for transmitting the nerve impulse from the atria to the ventricles
- Initiate impulses itself but at a slower rate than the SA node
What is the bundle of His (AV bundle)
- Mass of specialised fibres originate in the AV node
- Impulses travel down the bundle of his from node
- Bundle then branches off to the left and rigght wside of the heart
- The 2 branches then break up into fine fibres called the purkinje fibres
- this impules causes ventricular contraction
What is the cardiac cycle?
- Sequence of events in one heartbeat
- During every heartbeat the heart contracts and then relaxes
- The period of contraction is called systole
- The period of relaxation is diastole
