Week 2 Flashcards
Name the layers of structure of the vessels
- Tunica intima
- Tunica Media
- Tunica externa
Tunica Intima
Innermost layer containing endothelial cells - very smooth to minimise friction
Tunica Media
Middle layer of elastic and smooth muscle fibres. Much thicker in arteries. Allows for vasoconstriction/dilation
Tunica externa
Outermost layer. Constructed from connective tissue. these fuse with adjacent tissue to anchor vessel.
Elastic arteries
Largest in the body. Contain a higher proportion of elastic fibres in tunica media. Helps blood flow away from the heart (walls are distended during ventricular systole- recoil during ventricular diastole). Elastic fibres function as pressure reservoirs- stretched elastic fibres store mechanical energy which is converted into kinetic energy to push blood forward when the artery recoils. Hence, aorta is an elastic artery.
Muscular arteries
Distributing arteries. Tunica media contains more smooth muscle fibres than elastic. Greater ability to vasoconstriction/dilate. Continuous partial muscle contraction known as vascular tone (helps maintain pressure and blood flow as well as helps to shunt blood to specific areas).
Arterioles
Small arteries. Only 1-2 layers of smooth muscle cells. Regulate blood flow across capillary networks
Types of capillaries
- Continuous
- Fenstrated
- Sinusoid
Continuous capillaries
Most numerous
Found in CNS, lungs, muscle , and skin
Endothelial cells form a continuous tube
Fenestrated capillaries
Found in kidneys, small intestine villi, choroid plexus, ciliary process
Endothelial cells have small holes called fenestrations
Sinusoid capillaries
Found in liver, red bone marrow, spleen, ant. Pituitary, adrenal glands, parathyroid
Larger diameter
Can have larger fenestrations
Incomplete or no basement membrane
Large clefts between endothelial cells
Permit the passage of large proteins and blood cells.
What two factors is blood flow dependent on
- Pressure difference
- Vascular resistance
What is pressure difference
Blood flows from an area of higher pressure to lower pressure
What is vascular resistance
Caused by friction between the blood and vascular wall.
Dependent on 3 factors:
1. Lumen size of blood vessel (smaller size=increased resistance)
2.Viscosity of blood (increased viscosity= increased resistance)
3.Length of blood vessel (longer blood vessel= increased resistance)
What is blood pressure produced by?
Ventricular contraction
What factors affect vascular tone?
Differs between pulmonary and systemic circulations
Catecholamine actions differ due to receptor type
What is vascular tone?
the contractile activity of vascular smooth muscle cells in the walls of small arteries and arterioles
What factors increase blood viscosity
High haematocrit
Low deformability of RBCs
High Plasma viscosity
High fibrinogen concentration
Dehydration
What are the 3 methods of capillary exchange?
Diffusion
Transcytosis
Bulk flow
Diffusion in capillaries
Driven by concentration gradients
oxygen and nutrients:
They have higher concentration in blood and move down their concentration gradient into the interstitial fluid.
Carbon dioxide and wastes:
Higher concentration in cells and interstitial fluid, therefore diffuse into blood
Water soluble material diffusion pathway
Includes glucose and amino acids
Diffuse through intercellular clefts or fenestrations
Lipid soluble material diffusion pathway
Includes carbon dioxide, oxygen and steroid hormones.
Can pass directly through capillary endothelial cells
Plasma proteins and RBC diffusion pathway
Too large to pass through continuous or fenestrated capillaries
Can only pass through sinusoid capillaries
Transcytosis in capillaries
Material becomes enclosed inside a vesicle and enters the capillary cell via endocytosis. This pinocytic vesicle travels through the endothelial cell to the opposite surface and exits via exocytosis.
Used to transport insulin and maternal antibodies.
Bulk Flow in capillaries
Large amount of material transported in membrane structure. It is faster than simple diffusion but still relies on concentration gradients.
Blood hydrostatic pressure
Forces fluid out of the capillaries and into the interstitial fluid.
Interstitial fluid hydrostatic pressure
Pushes fluid from interstitial space into capillaries.
Blood Colloid Osmotic pressure
Attracts water from interstitial space into blood
Interstitial Osmotic Pressure
Draws water from the blood into the interstitial space.
Reperfusion Injury
Oxidative Stress: When blood flow returns, it often leads to the production of reactive oxygen species (ROS) such as superoxide anions and hydroxyl radicals. These ROS can cause extensive damage to cell membranes, proteins, and DNA.
Inflammation: Reperfusion can trigger an inflammatory response that exacerbates tissue damage. The influx of immune cells and the release of pro-inflammatory cytokines can further harm the tissue.
Calcium Overload: Reperfusion can cause an overload of intracellular calcium, leading to activation of various enzymes that break down cellular structures and worsen damage.
Endothelial Dysfunction: Damage to the endothelial cells lining blood vessels can lead to increased vascular permeability and contribute to tissue swelling and further injury.
Reoxygenation Injury
Production of ROS: The reintroduction of oxygen can lead to a burst of ROS production, which damages cellular components.
Mitochondrial Dysfunction: The mitochondria, which produce energy, can become overwhelmed by the sudden increase in oxygen and ROS, leading to dysfunction and cell death.
Metabolic Imbalance: Reoxygenation can disrupt cellular metabolism, leading to imbalances that can further damage cells and tissues.
Whaat does an increase in afterload indicate?
An increase in afterload indicates that the heart has to work harder to eject blood into the arteries. Afterload refers to the resistance the left ventricle must overcome to pump blood out into the systemic circulation.
What does an increase in preload cause?
An increase in preload indicates that there is an increase in the volume of blood that the heart must handle during diastole, the phase when the heart relaxes and fills with blood. Preload refers to the degree of stretch of the ventricular myocardium (heart muscle) just before contraction, influenced primarily by the volume of blood returning to the heart. This causes an increase in stroke volume
How many alveoli are there in the body
300 million
