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