Chapter 21 Flashcards
Arteries
Carry blood away from the heart
Has a thick muscular to elastic tunica media
High compliance
Two types elastic and muscular
What are the five main types of blood vessels?
Arteries, arteriole, capillaries, venules, and veins
Veins
Blood vessels that convey blood from the tissues back to the heart
Tunica interna
Forms the inner lining of a blood vessel and is in direct contact with the blood that flows through the lumen
Has an inner layer of endothelium and a basement membrane deep to the endothelium
Outer most layer between the tunica Interna and tunica media is the internal elastic lamina
Internal elastic lamina of the tunica interna
Thin sheet of elastic fibres with window like openings that facilitate diffusion of materials to the tunica media
Tunica media
Regulates the diameter of the lumen with vasoconstriction and vasodilation as well as vascular spasm to limit damage
Tunica externa
Outer covering of a blood vessel
consists of elastic and collagen fibres and contains nerves and blood vessels that supply tissue of the vessel wall called vasa vasorum
also helps anchor the tunica externa to surrounding tissues
Vasa vasorum
Small vessels that supply blood to the tissues of the vessels in the tunica externa
Elastic arteries
Largest arteries in the body
well defined internal and external elastic laminae
thick tunica media dominated by elastic fibres called elastic lamellae
the two major trunks that exit the heart are the aorta and the pulmonary trunk
Functions of the elastic arteries?
Propel blood onward while the ventricles are relaxing
walls stretch easily accommodating the surge of blood
elastic fibres momentarily store mechanical energy functioning as a pressure Reservoir
then they recoil and convert the stored energy in the vessel into kinetic energy of the blood
What is another name for elastic arteries and why?
Conducting arteries, because they conduct blood from the heart to medium sized more muscular arteries
Muscular arteries
Medium-sized arteries their tunica media contains more smooth muscle and fewer elastic fibres making the walls relatively thick
Tunica externa is often thicker than the tunica media
Functions of the muscular arteries?
Vasodilation and vasoconstriction
called distributing arteries because they distribute blood to each of the various organs
has the ability to maintain vascular tone
Stiffness in the vessel walls is important in maintaining vessel pressure and efficient blood flow
Anastomosis
Do union of branches of two or more arteries supplying the same body region
Collateral circulation
The alternative route of blood flow to a body part through and anastomosis
End arteries
Arteries that do not anastomose
Arterioles
Abundant microscopic vessels that regulate the flow of blood into the Capillery networks of the body tissues
have a thin tunica interna with a thin fenestrated internal elastic lamina that disappears at the terminal end
the terminal end of the arterial is called the metarteriole and tapers toward the Capillary junction
this junction the distal most muscle cell forms the precapillary sphincter which monitors the blood flow into the Capillary
Arterioles functions?
Play a key role in regulating blood flow from arteries into capillaries by regulating resistance
What is another thing arterioles are called?
Resistance vessels
Capillaries?
Smallest blood vessel, includes the microcirculation where blood from a metarteriole goes through Capillery’s into a post Capillary venule
What is the primary function of the capillaries?
Exchange of substances
What is something else the capillaries are called?
Exchange vessels
Vasomotion
Where blood flows intermittently through capillaries due to the alternating contraction and relaxation of the smooth muscle of metarterioles and the pre-capillary sphincters
Thoroughfare channels
Provides a direct route for blood from an arteriole to a venule bypassing capillaries
What are the three different types of capillaries?
- Continuous capillaries
- Fenestrated capillaries
- Sinusoids
Continuous Capillaries
The plasma membranes of endothelial cells form a continuous tube that is interrupted only by intercellular clefts, found in the central nervous system, lungs, muscle tissue, and skin
Fenestrated capillaries
Plasma membranes of the endothelial cells in these capillaries have many fenestrations and are found in the kidneys, villi of the small intestine, choroid plexus of the ventricles in the brain, ciliary processes of the eyes, and most endocrine glands
Sinusoids
Wider and more winding than other capillaries, unusually large fenestrations, and an incomplete or absent basement membrane, very large intracellular clefts that allow proteins and blood cells to pass from a tissue into the bloodstream
can be found in the red bone marrow and can contain special cells
Venules
Then walls that do not readily maintain shape drain the Capillery blood and begin the return flow of blood back towards the heart
Post capillaries venules
Initially receive blood from Capillery’s
Muscular venules
Post Capillery venules that acquire one or two layers of smooth muscle cells and the exchange of interstitial fluid can no longer occur
Veins
Composed of the same three layers as arteries but the tunica interna of veins is thinner the tunica media is thinner and the tunica externa is the thickest layer and consists of collagen and elastic fibres
Contain valves preventing backflow
Vascular (venous) sinus
A vein with a thin endothelial wall that has no smooth muscle to alter its diameter
surrounding dense connective tissue replaces the tunica media and tunica externa in providing support
Blood Reservoir’s
Systemic veins and venules function as blood reservoirs because they hold 64% of your body’s blood volume
Venoconstriction cause
During increase muscular activity the cardiovascular centre in the brain stem sends a larger number of sympathetic impulses to veins resulting in Venoconstriction
What are the three basic mechanisms that substances enter and leave capillaries?
- Diffusion
- Transcytosis
- Bulk flow
Diffusion through Capillaries?
Most important method of Capillery exchange
Used by oxygen, carbon dioxide, glucose, amino acids, hormones
Water soluble substances such as glucoseamine acid pass across capillary walls through intercellular clefts or fenestrations
Lipid soluble materials such as oxygen, CO2, and steroid hormones may pass across capillary walls directly through the lipid bilayer of endothelial cell plasma membranes
Transcytosis in capillaries?
Substance in blood plasma become enclosed within tiny penocytic vessicles that first enter endothelial cells by endocytosis then move across the cell and exit on the other side by exocytosis mainly important for large lipids insoluble molecules that cannot cross capillary walls in any other way such as insulin and antibodies
Bulk flow: Filtration and reabsorption
Passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction moves from an area of higher pressure to lower pressure
Filtration
Pressure driven movement of fluid and solutes from blood capillaries into interstitial fluid
Reabsorption
Pressure driven movement from interstitial fluid into blood capillaries
Net filtration pressure (NFP)
Determines whether the volumes of blood and interstitial fluid remain steady or change and is the balance of interstitial fluid osmotic pressure and blood colloidal osmotic pressure
Starlings law of the Capillaries
The volume of fluid and solutes reabsorbed normally is almost as large as the volume filtered the near equilibrium is starlings law of the capillaries
Blood hydrostatic pressure (BHP)
“Pushes” fluid out of capillaries into interstitial fluid
hydrostatic pressure is due to the pressure that water in blood plasma exerted against blood vessel walls
Interstitial fluid hydrostatic pressure (IFHP)
Opposing pressure of the interstial fluid
“pushes” fluid from interstitial spaces back into capillaries
close to zero mmHg
Blood colloid osmotic pressure (BCOP)
A force caused by the colloidal suspension of these large proteins in plasma that averages 26 mmHg in most capillaries
the effect is to “pull” fluid from interstitial spaces into capillaries
Interstitial fluid osmotic pressure (IFOP)
Opposing BCOP which “pulls” fluid out of capillaries into interstitial fluid .1 to 5 mmHg because only tiny amounts of protein are present in interstitial fluid
How is net filtration pressure calculated?
NFP=(BHP+IFOP)-(BCOP+IFHP)
Pressures that promote filtration - Pressures that promote reabsorption
Haemodynamics
Refers to the forces involved in circulating blood throughout the body
Blood flow
The volume of blood that flows through any tissue in a given time. Total blood flow is cardiac output the volume of blood that circulates through the systemic blood vessels each minute
What are the two factors that depend how the cardiac output becomes distributed into circulatory routes?
- Pressure differences
- Resistance
Blood pressure
The hydrostatic pressure exerted by blood on the walls of blood vessel
Systolic blood pressure
The highest pressure attained in arteries during systole
Diastolic blood pressure
The lowest arterial pressure during diastole
Mean arterial pressure (MAP)
The average blood pressure in arteries is roughly 1/3 of the way between the diastolic and systolic pressure’s
How can you calculate the map?
Map = diastolic BP + 1/3 (systolic BP - diastolic BP)
Vascular resistance relies on what three things?
- Size of the lumen - Smaller lumen equals greater resistance
- Blood viscosity - Higher the blood viscosity the higher the resistance
- Total blood vessel length - Longer vessels equal greater resistance
Systemic vascular resistance (SVR) also known as total peripheral resistance (TPR)
Refers to all of the vascular resistance is offered by the systemic blood vessels
Venous return
The volume of blood flowing back to the heart through the systemic veins occurs due to the pressure generated by contractions of the hearts left ventricle
What are the two other “pumps” of the body that help move blood from the lower body back to the heart?
- Skeletal muscle pump
- Respiratory pump
Circulation time
The time required for a drop of blood to pass from the right atrium through the pulmonary circulation, back to the left atrium, through the systemic circulation, down to the foot and back again to the right atrium, a resting person circulation time is normally one minute
Cardiovascular (CV) centre
Located in the medulla oblongata
helps regulate heart rate and stroke volume as well as controls neural, hormonal, and local negative feedback systems that regulate blood pressure and blood flow to specific tissues
receives input from higher brain regions and sensory receptors
Output from the cardiovascular centre flows along sympathetic and parasympathetic neurons of the autonomic nervous system
The three main types of sensory receptors that provide input to the cardiovascular centre are what?
- Proprioceptors
- Baroreceptors
- Chemoreceptors
Output for the cardiovascular centres sympathetic division travels along what?
Reaches the heart via the cardiac Excelerator nerves
Out put for the cardiovascular centres parasympathetic stimulation travels along what?
Vegas (X) nerves decrease heart rate
Output for the cardiovascular centre uses what nerves to communicate with smooth muscles in blood vessels?
Vasomotor nerves which controls vasocontraction or vasoconstriction called vasomotor tone
What are the two types of reflexes controlled by negative feedback loops regulated by BP?
Baroreceptor reflexes and chemo receptor reflexes
Baroreceptors
Pressure sensitive sensory receptors located in the aorta, internal carotid arteries, and other large arteries in the neck and chest
send impulses to the cardiovascular centre to help regulate blood pressure
The two most important baroreceptor reflex’s?
Carotid sinus reflects and aortic reflex
Carotid sinus reflex
Helps regulate blood pressure in the brain
nerve impulses propagate from the carotid sinus baroreceptors over sensory axons in the glossopharyngeal (IX) nerves to the cardiovascular centre
Aortic reflex
Regulates Systemic blood pressure nerve impulses from the aortic baroreceptors reach the cardiovascular centre via sensory axons of the vagus (X) nerves
when blood pressure falls the baroreceptors are stretched less and they send nerve impulses at a slower rate to the cardiovascular centre
When an increase in pressure is detected the baroreceptor send impulses at a faster rate increase in parasympathetic stimulation and decreasing sympathetic stimulation
Chemo receptors
Sensory receptors that monitor the chemical composition of blood are located close to the baroreceptors of the carotid sinus and arch of the aorta in small structures called carotid bodies and aortic bodies
Detect blood level changes of O2, CO2, hydrogen, decreased 02 =hypoxia, increased hydrogen = acidosis, excess CO2 = hypercapnia
Whore moans that help regulate blood pressure and blood flow by altering the cardiac output, Changing systemic vascular resistance or adjusting the total blood volume are?
- Renin angiotensin aldosterone system
- Epi-nephron and norepinephrine
- Antidiuretic hormone
- Atrial natriuretic peptide (ANP)
Renin angiotensin aldosterone (RAA) system
Blood volume decreases to the kidneys causing them to secrete renin into the bloodstream
Renin and angiotensin converting enzyme (ACE) act on their substrates to produce angiotensin two
Angiotension two Vasalconstricts blood vessels raising blood pressure by increasing systemic vascular resistance
Angiotensin two stimulates secretion of aldosterone which increases reabsorption of sodium and water by the kidneys increasing total blood volume which increases blood pressure
Epi-nephron and norepinephrine
Sympathetic stimulation causes adrenal medulla to release epi and norepinephrine increasing cardiac output by increasing rate and force of heart contractions
and causing vasoconstriction of arterials in veins and vasodilation of arterial’s in cardiac and skeletal muscle which helps increase blood flow to the muscle during exercise
Antidiuretic hormone
Produced by the hypothalamus and released from the posterior pituitary in response to dehydration or decrease blood volume
causes vasoconstriction which increases blood pressure
also promotes movement of water from the lumen of kidney tubules into the bloodstream resulting in increased blood volume and decreased urine output
Atrial natriuretic peptide (ANP)
Released by cells in the atrium of the heart lowers blood pressure by causing vasodilation and by promoting the loss of salt and water in the urine which reduces blood volume
Auto regulation
The ability of a tissue to automatically adjust his blood flow to match is metabolic demands
What are the two general types of stimuli that cause auto regulatory changes in blood flow?
- Physical changes
- Vasal dilating and vasal constricting chemicals
Systolic blood pressure
The force of blood pressure on arterial walls just after ventricular contraction
Diastolic blood pressure
The force exerted by the blood remaining in arteries during ventricular relaxation
Korotkoff sounds
Various sounds that are heard will taking blood pressure
Pulse pressure
The difference between systolic and diastolic pressure
Shock
Failure of the cardiovascular system to deliver enough 02 and nutrients to meet cellular metabolic needs
What are the four types of shock?
- Hypovolaemic shock
- Cardiogenic shock
- Vascular shock
- Obstructive shock
A common cause of hypovolaemic shock?
Acuter sudden haemorrhage
Cardiogenic shock?
The heart fails to pump adequately most often because of myocardial infarction
What are the different types of sharks included in vascular shock?
Anaphylactic shock, neurogenic shock, septic shock
Obstructive shock
Occurs when blood flow through a portion of the circulation is blocked most common cause is pulmonary embolism
What are the four main negative feedback systems that compensate for shock?
- Activation of the renin angiotensin aldosterone system
- Secretion of antidiuretic hormone
- Activation of the sympathetic division of the ANS
- Release of local vasodilators
What are signs and symptoms of shock?
- Systolic blood pressure is lower than 90 mmHg
- Resting heart rate is rapid due to sympathetic stimulation and increase blood levels of Epinephrine and Norepinephrine
- Pulses week and rapid due to reduced cardiac output and fast heart rate
- Skin is cool pale and clammy due to sympathetic constriction of skin blood vessels and sympathetic stimulation of sweating
- Mental state is alter due to reduced oxygen supply to the brain
- Urine formation is reduced due to increase levels of aldosterone and antidiuretic hormone
- The person is thirsty due to loss of extra cellular fluid
- The pH of blood is low (acidosis) due to the buildup of lactic acid
- The person may have nausea because of impaired blood flow to the digestive organs from sympathetic vasal constriction
All veins of the systemic circulation drain into what?
Superior vena cava, inferior vena cava, or coronary sinus
Aorta
Largest artery of the body and has four principal divisions ascending aorta, arch of the aorta, thoracic aorta, and abdominal aorta
Abdominal aorta
Descends to the level of the fourth lumbar vertebrae where divides into two common iliac arteries which carry blood to the pelvis and lower limbs
The unpaired visceral branches arise from the anterior surface of the aorta and include the coeliac trunk and the superior mesenteric and inferior mesenteric artery’s
The paired visceral branches arise from the lateral surfaces of the aorta and include the suprarenal, renal, and gonadal artery’s
Ascending aorta
Contains three dilations called aortic sinuses
right and left sinuses give rise to the right and left coronary arteries
the right and left coronary arteries arise from the ascending aorta just superior to the aortic valve forming a crown like ring around the heart
giving off branches to the atrial and ventricular myocardium
Arch of the aorta
Three major arteries branch from the superior aspect of the arch of the aorta the brachiocephalic trunk, the left common carotid, and the left subclavian
Brachiocephalic trunk
The first and largest branch from the arch of the aorta
Extend superiorly bending slightly to the right and divides at the right sternal clavicular joint to form the right subclavian artery and right common carotid artery
Left common carotid artery
The second branch from the arch of the aorta which divides into the same branches with the same names as the right common carotid artery
Left subclavian artery
The third branch from the arch of the aorta which distributes blood to the left vertebral artery and vessels of the left upper limb similar in distribution and name to those branching from the right subclavian artery
Thoracic aorta
Begins at the level of the intravertebral disc between the fourth and fifth thoracic vertebrae where it lies to the left of the vertebral column
How does the abdominal aorta end?
By dividing into the right and left common iliac arteries
which intern divide into the internal and external iliac arteries
which then become the femoral arteries in the thighs, the popliteal arteries posterior to the knee, and the anterior and posterior tibial arteries in the legs
What are the three systemic veins that return deoxygenated blood to the heart?
Coronary sinus, superior vena cava, inferior vena cava
What are the three pairs of veins that most blood draining from the head passes through?
Internal jugular external jugular and vertebral veins
What are the deep veins of the upper limbs?
Brachiocephalic veins: subclavian vein’s, axillary veins, brachial vein’s
What are the superficial veins of the upper limbs?
Cephalic vein’s and basilic vein’s
Hepatic portal circulation
Carries venous blood from the gastrointestinal organs and spleen to the liver
Portal vein
Carries blood from one Capillery network to another
Hepatic portal vein
Receives blood from capillaries of gastrointestinal organs and the spleen and delivers it to the sinusoids of the liver
Pulmonary trunk
Emerges from the right ventricle and passes superiorly, posteriorly, and to the left
divides into two branches right pulmonary artery to the right lung, and left pulmonary artery to the left lung
