Module 15: Vascular System Flashcards
What is the role of arteries?
Carry blood away from the heart
What is the role of veins?
Return blood to the heart
What is the role of capillaries?
Connect the smallest arteries to the smallest veins
What is the role of conducting arteries (elastic arteries)?
Give examples
Expand as blood surges into them and recoil when the ventricles relax.
Ex. Aorta, common carotid artery, subclavian artery
known as muscular arteries - These arteries carry blood father way from the heart to specific organs and areas of the body. Examples: brachial, femoral, and renal arteries
Distributing arteries
Known as resistant vessels - Through the contraction of smooth muscle in their walls, they can resist the flow of blood, thus helping regulate blood pressure as well as control how much blood enters an organ. What artery is this and how are they connected?
Arterioles - Connected to capillaries by short connecting vessels called metarterioles
Veins become _______________ as they lead back to the heart
Converge, forming progressively larger and fewer vessels
What are three structural functions of the veins?
- Have thinner walls than arteries
- Have a great ability to stretch
- Can constrict extensively
Why are capillaries called the exchange vessels?
It’s within capillaries that nutrients, waste, and hormones are transferred between blood and tissues
What is the structure of capillaries?
Have extremely thin walls and very small diameters
Why do you precapillary sphincters open during exercise?
Muscles demand an abundance of blood.
When skeletal muscles require more oxygen, the precapillary sphincters open, blood fills the capillary network, and exchange of oxygen, nutrients, and wastes occurs with the tissue fluid.
What happens to precapillary sphincters when the body is at rest?
They close. Blood bypasses the capillary bed and flows directly into a venule to begin its journey back to the heart and lungs
The walls of the capillary allow for?
Two-way exchange of substances and fluids
What do the mechanisms of exchange include?
Diffusion, filtration, and osmosis
What do capillaries release?
Chemicals, including oxygen, glucose, hormones, and nutrients that will be used by surrounding tissues
What do capillaries take up?
Waste such as carbon dioxide and ammonia.
Glucose, calcium, antibodies, and hormones - substances that need to be transported to other parts of the body.
What is diffusion?
Substances move from areas of greater to lesser concentration
What is the role of diffusion in capillary exchange?
Allows for the exchange of nutrients and waste products
On what end of the capillary bed does filtration occur?
Arterial side
What is the role of filtration in capillary exchange?
The higher pressure in the capillary pushes plasma and dissolved nutrients (such as glucose and amino acids) through the capillary wall and into the fluid in the surrounding tissues
The lower pressure allows proteins in the blood, such as albumin, to exert what’s known as
Colloid osmotic pressure
What is the role of albumin (protein) in colloid osmotic pressure?
Albumin in the blood pulls tissue fluid, along with the cells waste products, into the capillaries
What is the role of pulmonary circulation?
Routs blood to and from the lungs to exchange carbon dioxide for oxygen
What circulation system provides the lung tissue with oxygen?
Systemic circulation
Where does the exchange of oxygen for carbon dioxide occur?
The capillaries surrounding the alveoli
What is the role of systemic circulation?
Supplies oxygen and nutrients to organs and removes wastes
What vessel do all systemic arteries arise from?
Aorta
What main vessel supplies blood to the chest wall and the organs within the thoracic cavity?
Thoracic aorta
What main vessels supply blood to the pelvic organs, thigh, and lower extremities?
Common iliac arteries
Which vessel Supplies most of the small intestine and part of the large intestine?
Superior mesenteric artery
Why is it easier to feel the pulse at certain points on the body’s surface?
Each beat of the heart produces a surge of pressure that can be felt at points were an artery comes close to the body’s surface
What are the main arteries that supply the brain with blood?
External carotid artery and internal carotid artery
What is the role of the circle of Willis?
Helps ensure that the brain receives an adequate supply of blood
What is the body’s main vein?
Vena cava
What is the vena cava divided into, And where do you each of these veins receive blood from?
Superior vena cava (SVC) - Receives blood from the head, shoulders, and arms.
Inferior vena cava (IVC) - Receives blood from the lower part of the body
Blood from what area is drained into the internal jugular vein?
Receives most of the blood from the brain and face
The external jugular vein is more superficial. Blood is drained into this vessel from what areas?
The scalp, facial muscles, and other superficial structures
What areas of the body does the vertebral vein drain?
Cervical vertebrae, spinal cord, and some of the muscles of the neck
Veins from the digestive organs and spleen send their blood through the _______________ to the liver
Hepatic portal vein
What is the purpose of blood being processed in the liver before returning to the heart?
- allows the liver to remove excess glucose, which it then stores as glycogen
- Toxins, such as bacteria or alcohol, can also be partially removed before the blood is distributed to the rest of the body
What happens to blood pressure as it moves away from the heart?
Blood pressure declines until, in the vena cava, it is about 1 mm Hg
When cardiac output increases, blood pressure increases, when it decreases blood pressure decreases. What could cause increased/decreased cardiac output?
Exercising and then stopping exercising
What could cause blood volume to decline? What happens to the blood pressure?
Dehydration or a hemorrhage, blood pressure falls
When peripheral resistance is increased, what happens to blood flow and pressure?
Flow declines and pressure increases
What is the chief cause of increased blood viscosity?
An increased number of red blood cells, but it may also result from an increased amount of protein (albumin) or dehydration
What is the body’s chief way of dealing with increased peripheral resistance?
Adjusting the diameter of vessels
What effect would vasoconstriction have on blood pressure?
A reduction of the diameter of a vessel increases the resistance to bloodflow, and pressure rises (Blood flow into tissues decrease)
What effect would vasodilation have on blood pressure?
An increase in vessel diameter caused by the relaxation of vascular muscles decreases resistance to bloodflow. (Blood pressure declines and blood flow into the tissues increases)
Where does blood flow the fastest?
The aorta
Why has blood slowed considerably once it reaches the capillaries?
- Friction along the way has slowed the flow
- The smaller diameter of arterioles and capillaries has put up more resistance
- The number of vessels has become greater, giving capillaries a greater total cross-sectional area
- Capillaries are far removed from the left ventricle
Why is the slow blood flow beneficial in the capillaries?
Allows capillaries time to exchange nutrients, wastes, and gases with surrounding tissues
Why does velocity increase again when blood reaches the veins?
Veins have larger diameter is then capillaries, so they create less resistance
What is the role of the vasometer centre (area of the medulla)?
Sends impulses via the autonomic nervous system to alter blood vessel diameter, and therefore bloop pressure
What is the role of the baroreceptors in the carotid sinus and aortic arch?
Detect changes in blood pressure and transmit signals along the glossopharyngeal and vagus nerves to the cardiac control centre and the vasomotor centre in the medulla
If pressure is too high what happens?
- The medulla increases its output of parasympathetic impulses
- Vasodilation occurs, heart rate and stroke volume decrease
- Blood pressure drops
What happens if pressure is too low?
- the medulla Increases its output of sympathetic impulses
- Vasoconstriction occurs, heart rate and stroke volume increase
- Blood pressure rises
How does renin, angiotensin I, angiotensin II raise blood pressure?
Cause vasoconstriction and water retention through an interactive mechanism
How does aldosterone raise blood pressure?
Stimulates the kidneys to retain sodium - water follows sodium, increasing blood volume
How does antidiuretic hormone (ADH) raise blood pressure?
- Secreted by the posterior pituitary gland when the water content of the body falls
- Promotes vasoconstriction and water retention
How does epinephrine and norepinephrine raise blood pressure?
- Cause vasoconstriction
- Increases heart rate and force of contraction (epinephrine only)
How does atrial natriuretic peptide (ANP) Cause blood pressure to fall?
- Released by the hearts atria when elevated blood pressure stretches the walls of the heart
- Cause vasodilation
- Stimulates the kidneys to excrete sodium (and therefore water) reducing blood volume
