Tala Saleh. Riham Abu Arrah, Abdallah AlQawasmeh. Yanal Shafagoj

Transcription

1 27 Tala Saleh Riham Abu Arrah, Abdallah AlQawasmeh Yanal Shafagoj

2 Cardiovascular system Think of the following situation: 5 Cancerous cells (for example: Lymphoma cells) are placed in a proper medium with nutrients, they keep dividing as follows: Day 0: 5 Day 2: 500 Day 4: 0 Day 1: 50 Day 3: 5000 Cells kept dividing but by the 4 th day all died, because cells got crowded with not enough nutrients and a lot of waste products leading to their death, that s why the medium must be renewed and that s what the cardiovascular system idea is about. Cardiovascular system is composed of a heart and blood vessels, which permits the blood pumped from the heart to circulate in our body providing nourishment of the cells continuously. Total Body water By weight an average human adult has 60% water "approximately", so if a person weighs 70kgs, water will be distributed as follows: Total body water = 70kgs *60% = 42 L 2/3 * 42 L = 28 L "Intracellular fluid" 1/3* 42 L = 14 L "Extracellular fluid" 11 L "Interstitial fluid" 10 L in Gel form. 1 L Free form "Used in case of bleeding where fluid is taken from it and inserted into the blood". They are free of proteoglycan molecules (additional information)" 3 L "Plasma"

3 Blood volume Almost 7% of our weight is blood, so a typical adult has 70kgs*7% = 5L of blood, out of the 5L: 1) Pulmonary circulation has 0.8L Chambers of the heart: 0.35L Pulmonary vessels (Lungs): 0.45L 2) Systemic circulation has 4.2L Systemic veins: 3.2L Systemic arteries: 0.75L Capillaries: 0.35L Note: If blood leaves the vascular system, then we have bleeding (can be internal or external). Blood pressure and volume... V= Q/A V: velocity Q: Blood flow per minute A: Cross section area Q is always 5L/min while A differs among vessels, capillaries put together can reach up to 6000 cm2, which is a large area that's why the velocity reaches almost 0 in them.

4 "Blood pressure among different vessels" 0 mmhg 100 mmhg Heart 20 mmhg 85 mmhg 40 mmhg Circulation We have two types of circulation: 1) Systemic circulation Oxygenated blood flows from the left ventricle to all the tissues of our body except the lungs and returns to the right atrium. It can be called "Greater circulation" or "Peripheral circulation". 2) Pulmonary circulation Pulmonary arteries take deoxygenated blood away from the heart to the lung, while the pulmonary veins bring oxygenated blood from the lungs to the heart. It can be called "Lesser circulation" or "Central circulation"

5 Function of circulation: Supplies our body's tissues with the required nutrients and takes away the waste products. Circulation's Vessels: 1) Arteries 2) Arterioles: Small branches from the artery that release blood into the capillaries. 3) Capillaries: Exchange fluids, nutrients, etc. between the blood and the interstitial fluid. 4) Venules: They collect blood from capillaries and drain it into veins. 5) Veins Microcirculation It is the circulation of the blood in the smallest blood vessels of organs, composed of: 1) Arterioles. 2) Venules. 3) Capillaries. Capillaries: - Walls of the capillaries are extremely thin made of a single layer of endothelial cells, also they have no smooth muscles in their walls therefore cannot constrict nor dilate. - At their entrance there is a precapillary sphincter "A band of smooth muscles" that adjusts the blood flow into the capillaries by either constricting or dilating.

6 - Capillary exchange can be transcellular (through the cell), paracellular or intracellular in a bidirectional movement. - Have two ends; arterial and venous. Types of capillaries: 1) Glomerular Capillary Present in the kidney and shows only filtration. "Filtration: Bulk flow of the fluids from the capillary into the interstitial fluid". 2) Reabsorption Capillary Present in the GI tract and shows only reabsorption. "Reabsorption: Bulk flow of the fluids from the interstitial fluid into the capillary". 3) Other capillaries Present in skeletal muscles for example & show both reabsorption and filtration. Per day "Kidneys excluded" 20L of blood are filtered while 17L are reabsorbed, the remaining 3L are taken by the lymphatic capillary (Lymphatic capillary doesn't contain blood cells). Lymphatic capillary is a very thin walled vessel in the spaces between cells, it drains the ECF "3 L" into the systematic veins, if blocked they may cause edema (Accumulation of the 3L in the interstitial fluid causing swelling).

7 Note: If filtration increases due to the increment of permeability, driving force or both, it will cause edema. Starling Forces They are different forces that determine whether filtration or reabsorption in the capillaries will occur, they determine the bulk flow directionality and the rate at which the exchange occurs. They are 4 forces in total: 2 forces inside the capillary 2 forces outside the capillary The 4 forces are: The following are additional information not mentioned in the lecture 1) Hydrostatic pressure in the capillary (In). 2) Hydrostatic pressure in the interstitium (Out). 3) Oncotic pressure in the capillary (In). 4) Oncotic pressure in the interstitium (Out). Role of these forces in determining the bulk flow explained: The pressure exerted by blood against the wall of a capillary is called capillary hydrostatic pressure (CHP).The opposing hydrostatic pressure is called the interstitium hydrostatic pressure (IHP). Generally, the CHP originating from the arterial pathways is higher than the IHP, because lymphatic vessels are continually absorbing excess fluid from the tissues. Thus, fluid generally moves out of the capillary and into the interstitial fluid. This process is called filtration. The pressure created by the concentration of proteins in the blood is called the oncotic capillary pressure (OCP). OCP is higher than the interstitial oncotic pressure (IOP), because proteins are concentrated in the blood more than in the interstitium. Thus, water is drawn from the interstitial fluid back into the capillary. This process is called reabsorption.

8 The total force of the 4 forces (المحصلة) gives the net pressure and the direction of the flow "whether its filtration or reabsorption". Note: Bulk flow is the movement of fluids due to a pressure gradient. Note: what determines whether filtration increases or decreases is the driving force and the permeability. Note: Cardiac output is the volume of blood ejected from the heart (Left ventricle) per minute. Venous return is the volume of blood that returns to the heart (Right atrium) per minute, both usually 5L/min. Cardiac output and venous return are dependent on each other. Cardiac Output = Venous Return Histamine When allergy occurs, histamine is produced and 2 cases might happen: 1) Histamine increases permeability >> accumulation of fluids in the interstitial fluid >> Edema. 2) Histamine dilates the vein; increasing its area >> Blood volume is decreased >> Blood pressure is decreased >> No force to pull the blood up to the heart >> Death. Death occurred because there is no venous return therefore there is no cardiac output. Best Wishes