AnP Chapter 16 (LO6) Flashcards
Vascular System
Elaborate system of vessels to meet the need of a continuous supply of blood to provide tissues and organs and cells with oxygen and nutrients and remove waste products
The framework of the system consists of three types of blood vessels
Arteries carry blood away from the heart
Veins return blood to the heart
capillaries connect the smallest arteries to the smallest veins
Tunics
3 layers in the walls of both arteries and veins
Tunica intima, tunica media, and tunica externa
Tunica intima:
The innermost layer is exposed to the blood
Consists of a simple squamous epithelium called endothelium that is continuous with the endothelium that lines the heart
It’s Smooth surface keeps blood flowing freely without sticking to the vessel wall
Also produces chemicals that cause blood vessels to dilate or constrict
Tunica media:
also called elastic arteries
the middle layer is the thickest layer
compose a smooth muscle and elastic tissue it allows the blood vessels to change diameter
The smooth muscle in this layer is innervated by the autonomic nervous system
Tunica externa:
the outer layer is made of strong flexible fibrous connective tissue
This layer supports and protects a blood vessel
In veins this is the focus of three layers
In arteries it’s usually a little thinner than the middle layer
Arteries
Arteries carry blood away from the heart
Arteries closest to the heart of the largest and as they travel further away from the heart they branch and
divide becoming smaller
Arteries can be divided into conducting arteries, distributing arteries and arterioles
Conducting arteries
Examples aorta, common carotid artery, subclavian artery
Arterioles
the smallest arteries
Distributing arteries
These arteries carry blood father away from the heart to specific organs and areas of the body
also called muscular arteries
these arteries are smaller in diameter than elastic arteries
Examples brachial, femoral and renal arteries
Arterioles
Smallest arteries
Also called the resistance vessels because through the contraction of smooth muscle in their walls they can resist the flow of blood helping regulate blood pressure as well as control how blood enters an organ
Metarterioles
short connecting vessels that connect arterials to capillaries
Veins
Carry blood to the heart
Vessels closest to the heart are the largest
Veins are distinct from arteries in other ways:
the walls of veins are thinner
Veins have a great ability to stretch which allows them to carry varying amounts of blood with almost no change in pressure because of this they are sometimes called capacitance vessels
Veins can constrict extensively
Veins lie closer to the body’s surface
Large veins
Formed as medium sized veins converge these veins have a thick tunica externa
Examples: vina Cavae, pulmonary veins, internal jugular veins
Medium sized veins
Formed by the convergence of venules on the road toward the heart, medium size veins have thicker more elastic walls
These veins contain one way valves formed from thin endothelium
Examples radial and ulnar veins of the forearm, saphenous veins in the legs
Venules
These are the smallest veins and collect blood from Capillaries
The endothelium consists of squamous epithelium cells and acts as a membrane
tunica media is poorly developed giving venules thinner walls
They are porous and can exchange fluid with surrounding tissues
Fast fact
Veins contain more than 60% of blood in circulation in comparison arteries contain 11% the rest is contained in the lungs, heart and capillaries
Capillaries
Microscopic vessels that link arterials to venules
Within Capillaries nutrients, waste and hormones are transferred between blood and tissues
These are the exchange vessels of the circulatory system
which tissues contain a high number of capillaries?
Tissues with high metabolic rate such as the liver, kidneys and myocardium contain a large number of capillaries
which tissues contain a low number of capillaries?
Fibrous connective tissue such as tendons have a lower metabolic rate and contain fewer capillaries
which tissues contain no capillaries?
the upper dermis, cartilage, and the lens and cornea of the eye don’t have any capillaries
Capillary beds
networks that the pillars are organized into
Microcirculation
formed by capillaries to connect arterioles to venules
Precapillary sphincter
at the beginning of each capillary bed that regulates the flow of blood into the net work
Sinusoid
irregular blood-filled spaces are more permeable, allowing for the passage of large substances such as proteins and blood cells
This is how blood cells formed in bone marrow as well as clotting factors and other proteins synthesized in the liver enter the bloodstream
Liver, bone marrow and spleen contain these unique capillaries
Capillary Exchange
Capillary walls allow for 2 way exchange of substances and fluid
Capillary release chemicals including oxygen, glucose, hormones, and nutrients that will be used by surrounding tissues
capillaries take away carbon dioxide and ammonia
Diffusion
Most important mechanism of Capillary exchange substances move from areas of greater to lesser concentration
Blood flows into the capillaries from the arterial system carrying a supply of oxygen meaning the oxygen inside pillories is greater than in surrounding tissue fluid
As a result oxygen diffuses out of capillaries and into the surrounding fluid
Filtration and Colloid Osmotic pressure
Filtration Occurs close to the arterial side of the capillary bed
Osmotic pressure operates toward the venous side where about 85% of fluid is absorbed
Remaining 15% is absorbed by lymphatic system
Edema
accumulation of fluid when fluid filters out of the capillaries faster than its reabsorbed
3 main causes of edema
- Increase Capillary filtration: because Capillary pressure drives filtration arising Capillary pressure would increase filtration causing kidney failure, poor venous return from inactivity or failure of the right ventricle
- Reduced Capillary reabsorption: Hillary reabsorption depends on Albumin therefore a deficiency would slow reabsorption causing edema
- obstructive lymphatic drainage: and obstruction would cause fluid to accumulate
In general blood flows from …
the heart through arteries and capillaries and veins in back to the heart
portal system
in which blood flows through two networks of capillaries
The bodies main portal system occurs in the liver
anastomosis
when two vessels join together
Arteriovenous anastomosis
when blood flows directly from an artery to a vein
Venous anastomosis
blood flow from one vein to another vein
Pulmonary circulation
begins at the right ventricle and involves the circulation of blood through the lungs
systemic circulation
begins at the left ventricle and involves the circulation of blood through the body
Specialized circulatory systems
hepatic portal circulation (routes blood from the digestive organs to the liver), circulation to the brain and fetal circulation
Pulmonary Circulation
routes blood to and from the lungs to exchange carbon dioxide for oxygen
It doesn’t supply the lung tissue itself with oxygen those needs are met through systemic circulation:
how does pulmonary circulation work
- Blood leaves the right ventricle through the pulmonary trunk, which branch is in to the right and left pulmonary arteries
- The pulmonary arteries enter the lungs
- Pulmonary arteries branch into lobar arteries (one for each lobe of the lung)
a) These arteries branch into smaller and smaller arteries until ending at the capillary beds - Capillary surround the Alveoli where the exchange of oxygen for carbon dioxide occurs
- The capillaries form venules which merged to form veins
a) The veins merge until forming for pulmonary veins (two from each lung)
b) All for veins return oxygenated blood to the left atrium
In systemic circulation arteries carry ——– blood and veins carry ——— blood
In systemic circulation arteries carry oxygen rich blood and veins carry deoxygenated blood
pulmonary arteries carry ——blood to the lungs
pulmonary veins carry —-
however pulmonary arteries carry oxygen poor blood to the lungs
Once oxygenated pulmonary veins carry oxygen rich blood back to the heart for distribution to the body
Systemic circulation
Supplies oxygen and nutrients to organs and removes waste
Involves both arteries and veins
All systemic arteries arise either directly or indirectly from the aorta
Systemic circulation :
Aorta originates in the left ventricle and is divided into three regions and branches into several major arteries
Sending aorta
The aortic arch
Descending aorta
Sending aorta
rises a few centimetres above the left ventricle
Right and left coronary arteries branch off the ascending aorta to supply blood to the myocardium
The aortic arch
curves over the heart and turns downward behind the heart making an inverted U-shape
The aortic arch branches into three major arteries they include the:
Brachiocephalic artery
Common carotid artery:
Left subclavian artery:
Brachiocephalic artery:
Common carotid artery:
Left subclavian artery:
Brachiocephalic artery: which through it’s branches supplies blood to the head and right arm
Common carotid artery: extends into the neck
Left subclavian artery: supplies blood to the left shoulder and upper arm
Descending aorta
travels downward dorsal to the heart through the thoracic and abdominal cavities
Call the thoracic aorta above the diaphragm in the abdominal aorta below the diaphragm
The abdominal aorta branches into the right and left common iliac arteries
Common iliac arteries supply blood to the lower pelvis and leg
Peripheral Arteries
All systematic arteries arise either directly or indirectly from the aorta
The thoracic aorta and its branches supply the chest wall in the organs within the thoracic cavity
The abdominal aorta gives rise to the:
Celiac trunk
renal arteries
superior mesenteric artery
inferior mesenteric artery
Celiac trunk
renal arteries
superior mesenteric artery
inferior mesenteric artery
Celiac trunk: which divides into the gastric artery(supplies the stomach) the splenic artery (supplies the spleen) and the hepatic artery (supplies the liver)
Renal arteries: supply the kidneys
Superior mesenteric artery: supplies most of the small intestine and part of the large intestine
Inferior mesenteric artery: supplies the other part of the large intestine
The distal end of the abdominal aorta splits into…
the right and left common iliac arteries
Common iliac arteries
supply the pelvic organs thigh and lower extremities
Major arteries branching off the iliac arteries include the:
Internal iliac artery External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery Dorsalis pedis artery
Branching off the aortic arch is the:
Subclavian artery: supplies blood to the arm
Axillary artery: is the continuation of the subclavian artery in the auxiliary region
Brachial artery: the continuation of the axillary artery in the artery most often used for routine blood pressure measurement
Radial artery: which is often palpated to measure pulse
Two artery supplies blood to the brain
external carotid
internal carotid
The vertebral arteries arise from…
the right and left subclavian arteries
each extends up the neck through the cervical vertebrae and enters the cranium
The right common carotid artery arises from
the left common carotid arises from
the brachiocephalic
the aortic arch
At the level of Adams apple each common carotid branches into…
the external carotid artery and the internal carotid artery
external carotid artery
supplies most of the external head structures
Internal carotid
enters a cranial cavity and supplies to Orbits and 80% of the cerebrum
Circle of Willis
Circle of Willis is the circle of arteries which helps to ensure that the brain receives an adequate supply of blood
Peripheral Veins
Vein strain blood from the organs and other parts of the body and carry it to the vena cava which delivers it to the hearts right atrium
Superior vena cava(SVC)
which receives blood from the head, shoulders, and arms
Inferior vena cava(IVC)
which receives blood from the lower part of the body
Most of the blood of the Head and neck is drained by the
internal jugular, external jugular and vertebral veins
The great saphenous vein
longest vein in the body and is often harvested for use as graphs in coronary artery bypass surgery
The internal jugular
receives most of the blood from the brain as well as from the face
It merges into the subclavian vein and becomes the brachiocephalic vein which drains into the superior vena cava
External jugular vein
more superficial, drains blood from the scalp, facial muscles and other superficial structures
It also drains into the subclavian vein
The vertebral vein
drains the cervical vertebrae, spinal cord and some of the muscles of the neck
Hepatic Portal Circulation
Veins from the digestive organs and spleen don’t empty into the inferior vena cava rather they said their blood through the hepatic portal vein to the liver
how hectic portal circulation works
- Blood from the capillaries of the spleen, stomach, pancreas, gallbladder and intestines flows into superior mesenteric vein in the splenic vein which converge to form the portal vein
- The portal vein channels blood into the liver the blood is the distributed to the innumerable microscopic sinusoids (capillaries of the liver)
- Blood flows out of the sinusoids into the hepatic veins and from there into the inferior vena cava where it is returned to the heart
The purpose of the circulatory system
to deliver oxygen and nutrients to tissues and remove waste
As blood moves away from the heart blood pressure…
declines until it’s in the vena cava about 1 mm Hg
Blood pressure
the force exerted by the blood against the vessel wall
Blood pressure is determined by three factors cardiac output, blood volume, and resistance
cardiac output effect on blood pressure
Increase CO =Increase BP
Decreased CO=Decrease BP
blood volume effect on blood pressure
Decrease volume=Decrease BP
Increase volume=Increase BP
resistance effect on blood pressure
Increase resistance=Decrease flow and increase pressure
Decrease resistance=Increase flow and decrease pressure
Peripheral Resistance
The resistance to blood flow resulting from the friction of blood against the walls of vessels
The amount of friction depends on the viscosity of the blood in the diameter of a blood vessel
Blood viscosity
Viscosity refers to thickness or stickiness of blood the greater the viscosity the slower the flow vice versa
The chief cause an increase blood viscosity is an increased Number of red blood cells but it may also result from an increased amount of protein or dehydration
Vessel Diameter
The muscular layer of arterials allows them to constrict or dilate changing the amount of resistance to blood flow
Because blood viscosity remain stable and healthy individuals adjusting the diameter of vessels is the bodys before a controlling person or resistance and blood pressure
Vasomotion
adjusting the diameter of blood vessels
Vasoconstriction
production of the diameter of a vessel
Increases the resistance to blood flow because blood is being squeezed into a smaller space pressure rises
The amount of blood allowed to enter the vessels reduced blood flow into tissue decreases
Vasodilation
an increase in vessel diameter caused by the reaction of vascular muscles
Decreases resistance to blood flow blood pressure declines and blood flow into tissue increases
Atherosclerosis
A buildup of plaque in arterial walls that obstructs the opening and causes the arterial wall to deteriorate
Autoregulation
Refers to an organ’s ability to address blood flow with neutral or hormonal influence
Nitric oxide
is a powerful vasodilator secreted by endothelial cells which is used when tissues demand more blood
Endothelin’s
are powerful polypeptides vasoconstrictors
Reactive hyperemia
After being temporarily blocked blood flow to an area often dramatically increases
Neural Regulation of Blood Pressure
blood vessels also respond to input from the autonomic nervous system
Baroreceptors
in the carotid sinus and Eric arch detect changes in blood pressure and transmit signals along the glossopharyngeal and vagus nerves to the cardiac control center in the vasomotor center in the medulla
The vasomotor center
an area of the medulla in the brain sends impulses via the autonomic nervous system to alter blood vessel diameter and therefore blood pressure
If pressure is too high what does the medulla do
medulla increases its output of parasympathetic impulses
Basil dilation occurs heart rate and stroke volume decreases
Blood pressure drops
If pressure is too low what does the medulla do
The medulla increases its output of sympathetic impulses
Vasoconstriction occurs heart rate and stroke volume increase
Blood pressure rises
Renin, angiotensin I and angiotensin II
Raises BP
Cause vasoconstriction and water retention through an interactive mechanism
Aldosterone
raises BP
Secreted by the adrenal medulla when blood pressure falls
Stimulates the kidneys to retain sodium
Antidiuretic Hormone ADH
raises BP
Secreted by the posterior pituitary gland when the water content of the body falls
Promote vasoconstriction and water retention
Epinephrine and norepinephrine
raises BP
Credit by the adrenal medulla when the body is under stress
Cause vasoconstriction
Increases heart rate and force of contraction (epinephrine only)
Atrial natriuretic peptide (ANP)
raises BP
Released by the heart atria when elevated blood pressure stretches the walls of the heart
Causes vasodilation
Stimulates the kidneys to excrete sodium and therefore water reducing blood volume
Venous Return
After making its way through the arterial system blood must return to the heart
Because gravity pulls blood into the legs and away from the heart whatever someone stands veins must fight before to gravity to deliver blood back to the heart
Mechanisms aid in Venous return:
the skeletal muscle pump and the respiratory pump
Skeletal Muscle Pump
Muscles surrounding leg veins aid in venous return
Leg muscles contract a massage the veins in the legs propelling blood towards the heart
The valves in veins and share blood flows upward toward the heart
When the muscles relax blood flows backward pulled by the force of gravity
Blood puddles in valve flaps keeping the valve closed and preventing further backward flow
Respiratory Pump
The process of breathing also promotes the flow venous blood in the thoracic and abdominal cavities
During inhalation the chest expands in the diaphragm moves downward this causes the pressure in the chest cavity to drop and the pressure in the abdominal cavity to rise
The rising abdominal pressure squeezes the inferior vena cava forcing blood upward toward the thorax
Lower pressure in the thorax helps draw blood towards the heart
Valves in the veins in the legs ensure that blood doesn’t flow backward
