what is mean by blood vessels and its function?

Answer 1

The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively. The circulatory system is extremely important for sustaining life. Its proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system.

There are various kinds of blood vessels:

Arteries:
Arteries are muscular blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.


Aorta (the largest artery, carries blood out of the heart)
Branches of the aorta, such as the carotid artery, the subclavian artery, the celiac trunk, the mesenteric arteries, the renal artery and the iliac artery.

Arterioles:
An arteriole is a small diameter blood vessel that extends and branches out from an artery and leads to capillaries.


Capillaries (the smallest blood vessels):

Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm, which connect arterioles and venules, and are important for the interchange of oxygen, carbon dioxide, and other substances between blood and tissue cells.

Venules:
A venule is a small blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins.

Veins:
Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein. In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.

Venae cavae (the 2 largest veins, carry blood into the heart)

Answer 2

everything in our body has a function. Blood vessels have a function just like capillaries have a function just like veins have a function. Just look it up!

Answer 3

Arteries carry oxygenated blood under high pressures - so they have thickened muscular walls and small centres (lumens) and no valves. Veins carry slower moving deoxygenated blood so they have thinner walls and contain valves to prevent back flow of blood. Capillaries are designed to deposit the oxygen in the remotest parts of the body. They have thin walls - up to only 1 cell thick to allow diffusion of oxygen into tissues and waste carbon dioxide back into the blood.

Answer 4

blood vessels is blood conducting pipe and its function is help in the blood circulation

Answer 5

blood vessels is the tiny pipes in your body which transfer the red liquid throughout your body

Answer 6

The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.

structure :

All blood vessels have the same basic structure. The inner lining is the endothelium and is surrounded by subendothelial connective tissue. Around this there is a layer of vascular smooth muscle, which is highly developed in arteries. Finally, there is a further layer of connective tissue known as the adventitia, which contains nerves that supply the muscular layer, as well as nutrient capillaries in the larger blood vessels.

Capillaries consist of little more than a layer of endothelium and occasional connective tissue.

When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis (pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages.

Laid end to end, the blood vessels in an average human body will stretch approximately 62,000 miles--2.5 times around the earth.

types of blood vessels :

There are various kinds of blood vessels:

* Arteries
* Aorta (the largest artery, carries blood out of the heart)
* Branches of the aorta, such as the carotid artery, the subclavian artery, the celiac trunk, the mesenteric arteries, the renal artery and the iliac artery.
* Arterioles
* Capillaries (the smallest blood vessels)
* Venules
* Veins
* Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein.
* Venae cavae (the 2 largest veins, carry blood into the heart)

They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart. The term "arterial blood" is nevertheless used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen.

functions :

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis), but arteries - and veins to a degree - can regulate their inner diameter by contraction of the muscular layer.This changes the blood flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation.

Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100%) with oxygen. In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 70%. (The values are reversed in the pulmonary circulation.)

The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg.

Vasoconstriction is the constriction of blood vessels (narrowing, becoming smaller in cross-sectional area) by contracting the vascular smooth muscle in the vessel walls. It is regulated by vasoconstrictors (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandins), a number of hormones (e.g. vasopressin and angiotensin) and neurotransmitters (e.g. epinephrine) from the nervous system.

Vasodilation is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide (termed endothelium-derived relaxing factor for this reason).

Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins, which leads to most of the symptoms of inflammation (swelling, redness and warmth).

their role in diseases:

Blood vessels play a role in virtually every medical condition. Cancer, for example, cannot progress unless the tumor causes angiogenesis (formation of new blood vessels) to supply the malignant cells' metabolic demand. Atherosclerosis, the formation of lipid lumps (atheromas) in the blood vessel wall, is the prime cause of cardiovascular disease, the main cause of death in the Western world.

Blood vessel permeability is increased in inflammation. Damage, due to trauma or spontaneously, may lead to haemorrhage. In contrast, occlusion of the blood vessel (e.g. by a ruptured atherosclerotic plaque, by an embolised blood clot or a foreign body) leads to downstream ischemia (insufficient blood supply) and necrosis (tissue breakdown).

Vasculitis is inflammation of the vessel wall, due to autoimmune disease or infection.

Answer 7

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Answer 8

Heart --> Arteries--> Arterioles ---> Capillaries---> Venules ---> Veins ---> Heart

Vessel Wall Anatomy: 3 layers (except capillaries)

Tunica intima (interna) - endothelial lining
Tunica media - smooth muscle innervated by vasomotor fibers.
Tunica adventitia (externa) - outermost, loose fibrous connective tissueArteries: Carry blood away from heart.
Elastic Arteries: have elastic connective tissue in t. media. Withstand large pressure changes. Elastic recoil is important in smooth blood flow.

Muscular Arteries: smaller arteries near organs. More smooth muscle in tunica media.

Arterioles: Smallest, thinnest arterial vessels. Feed capillary beds and major site of blood flow regulation in tissues.

Capillaries: Most numerous (1.2 billion). 1,000 square miles of potential surface area. But have only 4-5% of body's blood at rest. Thin walled - only have tunica intima. Site of gas and nutrient exchange with tissues.

Continuous or fenestrated.
Thoroughfare capillaries or channels - direct link between arteriole and venule.
True capillaries - Flow into them is regulated by pre-capillary sphincters.
Sinusoids - large, distended capillaries found in lymphatic system (spleen), bone marrow, pituitary, and liver. Sites where phagocytosis and secretion is important.
Venules: Smallest venous vessels. Smallest ones have no tunica media.

Veins: Three distinct tunics. Low pressure system. Blood flow to heart aided by skeletal muscle pump, respiratory pump, and one-way valves. Contain 65% of body's blood at rest.

Varicose veins -- due to stretching of veins and weakening of valves.


Historical Note: William Harvey's Demonstration of Valve Function

Physiology of Circulation

Blood Flow = amount of blood flowing thru a vessel or organ. Varies according to local factors and neural (ANS) regulation.

Blood Pressure = force per unit area exerted on vessel wall. Expressed in mmHg.

Resistance = opposition to flow; friction.

Major determinants of resistance are:

blood vessel diameter
vessel length
viscosity of blood.
Resistance is proportional to 1/(radius)4 -- i.e., if radius is doubled or halved, resistance is decreased or increased 16 fold.

Viscosity and vessel length don't change much in the short term, so vessel diameter is the major factor determining resistance.

Flow = D Pressure/Resistance

Systemic Blood Pressure

Systolic arterial pressure: maximum pressure exerted by left ventricle.

Diastolic arterial pressure: minimum pressure in vessels.

Mean arterial pressure = Diastolic pressure + 1/3(SP - DP). Note: this is not a straight average since diastole lasts longer than systole.

Blood pressure drops primarily in the arterioles because of the numerous fine branches that increase the total cross-sectional area of vascular bed.

Blood Pressure = cardiac output X TPR

Anything that influences cardiac output or resistance will affect blood pressure.

Regulation of Blood Pressure

Nervous System Control:

Vasomotor fibers of SNS
Vasomotor center of medulla oblongata
Pressoreceptors (Baroreceptors) in aortic and carotid sinuses
Chemoreceptors (oxygen and pH)
Hypothalamic
Cortical: Cerebral cortex ("higher thought processes") can affect blood pressure
Chemical Control:

Epinephrine and Norepinephrine from adrenal medulla.
Atrial natriuretic factor - increase in BP promotes reduction of blood volume and pressure by increasing secretion of sodium.
Antidiuretic hormone
Kidney's renin-angiotensinogen aldosterone system (RAAS)
Aldosterone - adrenal cortex. Promotes sodium retention. Hyperaldosteronism

Variations in Blood Pressure

Measurement of blood pressure is usually by ausculatory methods. These methods rely on turbulence of blood flow causing detectable sounds.

Classical (using the Sounds of Korotkoff) method is use of sphygmomanometer. Inflated cuff blocks blood flow thru brachial artery. When external cuff pressure is high enough to just stop flow --> systolic arterial pressure. When cuff deflated, blood begins to flow thru artery, but flow is turbulent and can be detected with stethoscope. When blood flow just becomes quiet (laminar flow of blood) --> cuff pressure equals resting pressure in artery --> diastolic arterial pressure.

Normal Range for Blood Pressure:

110-140 mmHg systolic

75-80 mmHg diastolic.

Hypotension: systolic pressure < 100 mmHg. Very relative. Some chronic conditions lead to hypotension.

Orthostatic hypotension: sudden change in posture -- blood wells up in lower extremities --> blood pressure drops --> blood flow to brain slows --> dizziness.

Age & medications (esp. beta blockers) affect orthostatic hypotension.

Hypertension: Persistent systolic pressure > 150 mmHg and/or diastolic > 90 at rest. Damaging to vessels, kidneys in particular.

Multiple causes.
Obesity: increase in vessel lengths (to serve fat) --> increase in resistance.
Atherosclerosis -- decrease in vessel diameter due to fat deposits.
Arteriosclerosis -- hardening of arteries (less elastic recoil)
Sodium retention. Increases blood volume. Genetic factors/race differences -- relates to gender and racial differences in responses to various hypertension medications.
Stress/Lack of exercise.
Diet
Blood Flow

Delivery of blood depends on metabolic "needs" of tissue.

How is "need" recognized by body?

Flow is proportional to Pressure/Resistance

Change in cross sectional area is the major determinant

Capillary Dynamics

Exchange of nutrients relies primarily on diffusion.

Rate of diffusion will depend on permeability of capillaries and capillary pressures.

Permeability differences
Presence or absence of fenestrations.
Blood-brain barriers
Two Key Pressures:

Hydrostatic pressure or filtration pressure:
Osmotic or Oncotic Pressure
Normal pressure difference results in net fluid movement into capillary. For delivery of nutrients to tissues, there must be net fluid movement out of capillary, so net hydrostatic pressure must be greater than net osmotic pressure.

Excess interstitial fluid is recovered by lymphatic system. Edema.

Circulatory Shock: inadequate blood flow to meet metabolic needs of tissues.

From:

Blood or fluid loss (hypovolemic)
Excessive vasodilation
Heart failure (cardiogenic)
Pulmonary Circulation

Low pressure system

Blood flow must be slower and exert less pressure on fine capillaries.

Right Ventricle (low oxygen blood) --> Pulmonary Trunk --> Pulmonary arteries --> lobar arteries -->arterioles --> capillaries surrounding alveolar sacs --> pulmonary venules and veins (high oxygen blood--> left atrium --> systemic circulation.

Hepatic Portal System

Transports blood from visceral (spleen, stomach and intestines) organs to liver--> blood then goes to heart.

Principal Systemic Arteries

Ascending Aorta
Brachiocephalic
Rt subclavian
Axillary
Brachial
Radial and Ulnar
Palmar arch and digitalsRt common carotid
Internal carotid--corotid sinus at base (baro- & chemo-receptors)
External carotid
Facial & neck arteries
Left common carotid: like right common carotid
Left subclavian: like right subclavian
Thoracic Aorta
Thoracic musculature and organs--diaphragm, esophagus, intercostals, bronchials.
Abdominal aorta
Abdominal viscera--renals, mesenteric, gonadals.
Common iliacs
Internal iliac
External iliac
Deep femoral
Femoral
Popliteal
Tibial (anterior and posterior)
Peroneal
Plantar and digitals

Principal Veins
Superior Vena Cava
Left & Right Brachiocephalic
External and Internal jugulars
Cranial and facial vessels
Subclavians (left and right)
Axillary
Cephalic & basilic (superficial)
Median cubital (venipuncture site)
Brachial (deep)
Radial & Ulnar
Inferior Vena Cava: Thoracic, then abdominal portions--branch to form:
Left and Right Common Iliacs
Internal iliac
External iliac
Deep femoral
Femoral
Popliteal
Anterior and Posterior Tibial
Plantar veins
Great Saphenous (superficial-anterior)
Small Saphenous (superficial-posterior)
Saphenous Vein Commonly Used for Coronary Bypasses
* Internal mammary artery is increasingly used