General Anatomy (Introduction To The Circulatory System And Lymphatic System) Flashcards
What does the circulatory system do?
The circulatory system transports fluids throughout the body & thus it
• Provides the oxygen (O2) & nutrients to the organs, muscles & tissues; keeps them healthy and alive.
• Helps the body to get rid of carbon dioxide (CO2) & metabolic waste products.
What are the two types of circulatory system?
Circulatory system consists of cardiovascular (blood circulation) and lymphatic circulation.
• Blood circulation:
– Heart pumps the blood into blood vessels (vascular system).
– Blood vessels (artery, capillary, vein) are the transportation network throughout the
body.
• Lymph circulation:
– Lymphatic vessels
– Lymph nodes
What are the two types of blood circulatory system?
• Closed circulatory system: Blood is circulated through vessels such as arteries, capillaries, veins.
• Open circulatory system: Through the capillary wall blood pass through & fills the body interstitial (intercellular) space, where tissues & cells directly bathe (e.g., in spleen).
What is pulmonary circulation?
- Portion of cardiovascular system
- Pulmonary circulation moves blood between the heart and the lungs.
- It transports deoxygenated blood via the pulmonary artery to the lungs to absorb oxygen and release carbon dioxide.
- The oxygenated blood then flows back to the heart through pulmonary veins.
What is the systemic circulation?
- Portion of cardiovascular system
- Systemic circulation moves blood between the heart and the rest of the body.
- It sends the oxygenated blood out to cells via arteries (Away from the heart to the body).
- Returns deoxygenated blood to the heart by the veins.
What is the coronary and the foetal circulation?
➢ Coronary circulation: for the heart only
➢ Foetal circulation is in embryonic & foetal period.
What are the 3 layers of tunics in the wall of vessels?
- tunica intima (innermost)
- tunica media - thicker in arteries than in vein
- tunica adventitia (outer)
What is the tunica intima?
Endothelium: Simple squamous epithelium
Subendothelium: Loose connective tissue, few smooth muscle
Internal elastic lamina: Elastic fibers
What is a tunica media?
Connective tissue fibers & Smooth muscle
What is the tunica adventitia?
Connective tissue fibers
Connective tissue cells
How does the structure of arteries and vein changes?
• The structural changes in the wall of different types of arteries or veins are gradual.
• No sharp demarcation is there.
What is the process of atherosclerosis (hardening) of arteries?
• Deposition of cholesterol within smooth muscle cells & macrophage (foam cell) in
subendothelium.
• Proliferation of smooth muscle cell & connective tissue elements
• Later the calcium deposit forms an atheromatous plaque (atheroma).
• Well-demarcated, hardened yellow areas or swellings on the intimal surfaces of arteries.
• Focal thickening of intima & narrowing of the lumen of the vessels
• Loss of elasticity of the arterial walls
• Focal thickening of intima→surface irregularity may result in thrombosis & may occlude the artery.
• This thrombus may also be flushed into the bloodstream and block smaller vessels distally as an embolus.
• The consequences of thrombosis & embolus from atherosclerosis include ischemia (reduction of blood supply) and infarction (local death, or necrosis).
• These are particularly significant in the
Heart (ischemic heart disease and myocardial infarction or heart attack), Brain (stroke), and
Distal parts of limbs (gangrene/necrosis).
What are arteries?
- Carry blood from the heart under a relatively high pressure
- The further they are from the heart the less caliber they will have, and therefore the different types of arteries are distinguished from each other depending on their overall size, the amount of muscle in tunica media.
What are the three types of arteries?
- muscular arteries
- elastic arteries
- arterioles
What are the muscular arteries? (Medium arteries)
- Medium muscular arteries, the wall has a circular pattern deposited smooth muscle which enables it to control its diameter.
- Decrease the diameter to regulate the blood distribution to the body.
- Most of them are named arteries, e.g. brachial and femoral arteries.
What are elastic arteries? (Large arteries)
- Large elastic arteries, have many elastic layers in their walls (subendothelial layer, tunica media) they receive the cardiac output, they include:
a) aorta
b) brachiocephalic trunk c) subclavian
d) carotid arteries
e) pulmonary trunk. - Their elasticity enables them to receive the high blood pressure from the ventricle, reduce the pressure and return to their normal size.
- They expand as the pressure increases, and when the ventricles relax they will constrict and return to their normal size; and maintain the blood pressure within the circulation.
What are arterioles? (Small arteries)
- Thick wall in relation to its lumen
- Tunica media entirely made up of smooth muscle
- The pressure within the arterial vascular system is controlled by the arterioles muscle tonus
- The filling of the capillary bed is regulated by the level of contraction of the muscular layer in the arterioles. Hypertension will result if their walls are over constricted.
Arterioles and small arteries are not named.
What are capillaries?
- Microscopic blood vessels in the form of network connecting the arteriole and the venules
- Usually less than 1 mm long. They have selective permeability
- Tunica intima made up of single layer endothelium (no media, no adventitia)
What are the three type of capillaries?
- continuous
- fenestrated
- sinusoids
What is the function of the capillaries?
- Providing nutrients and oxygen to the surrounding tissue
- Absorption of nutrients, waste products and carbon dioxide
- Excretion of waste products from the body
Where are continuous capillaries found?
Muscle and brain
Where are the fenestrated capillaries found?
Pancreas, Thyroid gland, renal glomeruli
Where are the sinusoid capillaries found?
Liver and spleen
What are veins?
- Veins (except for the pulmonary vein) transfer the low-oxygenated blood from the capillary bed to the heart
- Due to its low oxygen content; the blood will be dark in color.
- The veins walls are thinner (specially in the tunica media) than those of the arteries due to the low blood pressure.
- They don’t pulsate.
What are the three types of veins?
- large veins
- venules
- medium veins
What are large veins?
Large veins, have wide bundles of longitudinal smooth muscles with a well developed tunica adventitia.
What are venules?
- Smallest veins that drain the capillary bed
- Join each other to form small veins
- Small veins drain into larger veins which will form venous plexuses
What are medium veins?
- Drain the venous plexuses
- Accompany the medium arteries
- Have passive flap valves that permits the blood to flow towards the heart (opposite to the gravity) and not to reverse direction
- Cephalic, basilic and saphenous veins
What is anastomosis?
- Communication between adjacent arteries
- Helps to provide multiple detours (pathways) for blood flow in case one of the main branches become obstructed
- Obstruction due to a compression caused by pathology or due to a compression by a joint position.
What is the function of anastomoses?
If the main passage was closed, alternative smaller pass ways will increase in size and even proliferate in number; a process that may take some time to take place and compensate for the less blood supply to the affected area.
What are end arteries?
- True (anatomic) end arteries do not anastomose with adjacent arteries
- Occlusion of a true end artery interrupts the blood supply to the structure or segment of an organ it supplies
- Eg: The end artery to the retina, the occlusion of which will result in blindness. - Functional end arteries
- Arteries with ineffectual anastomoses
- Calibre of anastomosis is insufficient to keep tissue perfused
- Supply segments of the brain, liver, kidneys, spleen, and intestines; they may also exist in the heart.
E.g: Stroke, Heart Attack
What are venae comitantes?
- Veins accompanying deep arteries
- Double or multiple in number
- Surround arteries in an irregular branching network
- Act as a counter-current heat exchanger that will warm up the venous blood returning to the heart from the cold limbs
What is the cavernous tissue?
- Is an endothelial lined, blood filled tissue, and is surrounded by smooth muscles.
- This tissue has an erectile characteristics. - Present in the male’s penis and in the clitorisliver
What is portal circulation?
- Normally, the artery supplying an organ ends in a set of capillaries, then blood is collected by veins.
- Portal system, the veins from an organ enter another organ where they divide into another set of capillaries
What is the hepatic portal venous system?
- Circulation of blood from the small intestine, the right half of the colon, and the spleen through the portal vein to the liver
E.g: - Coming from the heart, the arteries will supply the digestive tract (large intestines, small intestines)
- It will go into the capillary bed and drain into the veins that go to liver.
- In the liver, it will be separated into capillaries again before it drains back into the proper veins.
What is the lymphatic system?
- A network of lymphatic vessels forms a one-way system that carrieslymphtowardstheheart.
- Consists of two semi-independent components
1. Extensive network of lymphatic vessels - Return extra fluid from the tissue spaces to the vascular system [The one that has not been fully drained by the veins. It will go into the lymphatic vessels -> Heart]
2. Various lymphoid tissues (lymph nodes, - spleen, thymus) Involve in the immune defense
What is the function of the lymphatic system?
- Draining excess interstitial fluid into the systemic vessels
- Transporting dietary lipids from the digestive system
- Facilitating immune responses by production of lymphocytes & antibodies
- Note: lymphatic vessels are found in all tissues & organs of the body except the CNS, eye ball, internal ear, epidermis of the skin, teeth, cartilage & bone.
What is the lymph?
Is the tissue fluid once it has entered the lymphatic vessels
What is the process of the lymph system?
- Coming from the heart, the Arteries -> Arterioles -> Capillaries
- Interstitial fluid will go into the interstitial space
- Not all of the fluids will return back to the venules because some of them will accumulate and will drain into the lymphatic capillaries
- The interstitial fluid will enter lymphatic capillaries and will drain into the lymphatic vessels
- Once the interstitial fluid enters the lymphatic capillaries, the fluid is called lymph.
- The lymph will go into the lymphatic vessels -> Lymphatic trunk (Combination of vessels) -> Lymphatic Duct (Combination of trunks) -> It will end into the angle of the subclavian vein and IJV
- Before lymph is returned to the blood stream, it passes to the lymph node.
- The lymph vessels that carry lymph to lymph node are referred to as Afferent vessel
- The lymph vessels that carry lymph away from a lymph node are Efferent vessel
- The lymph reaches the blood stream at the root of the neck by RT lymphatic duct and thoracic duct
What is the thoracic duct?
- Begins in the abdomen at the level of the second lumber vertebra – cisterna chyli
- Traverses the aortic opening in the diaphragm - Ends into the left subclavian vein near its junction with left internal jugular
- Receives lymph from the lower limbs, pelvic cavity, abdominal cavity, left side of the thorax, left side of the head & neck & left upper limb.
- Important because it receives lymph from most part of the body.
What does the right lymphatic duct do?
Rt lymphatic duct receives lymph from the Rt part of thorax, upper limb, head & neck Tunica adventitia
