BODY System Lecture 5 - Niggy Gouldsborough PDF

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Niggy Gouldsborough ...

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BODY SYSTEMS STRUCTURE OF BLOOD VESSELS LECTURE 5 BLOOD VESSELS:           

All tissues have an arterial supply (which brings oxygen and nutrients) and a venous drainage (which takes blood containing waste products to the heart) Blood vessels are there to make sure that all our tissues and organs have a blood supply to get nutrients and oxygen Also, our organs and cells need to have a venous drainage that’ll take blood which contains waste products away from cells to the heart We have different types of blood vessels e.g. large, small, narrow The largest artery in the body is the aorta which carries blood away from the heart The aorta then leads into smaller (but still big) arteries which lead to arterioles which lead to capillaries Capillaries are the site where nutrient exchange take place Oxygen and nutrients are transferred to cells from capillaries Capillaries are located within tissues Leading from capillaries are venules which lead to veins which then leads to the inferior vena cava Superior/ Inferior vena cava is the largest vein in the body

THE DIFFERENT TYPES OF BLOOD VESSELS EACH HAVE DIFFERENT FUNCTIONS All blood vessels must:   

be resilient Be flexible (as we’re compressing them when we move a little bit) Always stay open

BLOOD VESSEL STRUCTURE:    

Hollow centre in blood vessel is called the lumen The next layer is the tunica intima which is the inner layer of the blood vessels (layer surrounding the wall of the lumen) also thinnest layer (Endothelium = simple squamous) The following layer the Tunica media Last layer is the tunica adventia

Tunica intima    

Thinnest layer made from endothelium Endothelium- simple squamous epithelium The tunica intima is the Basal lamina of the epithelial cells Sub-endothelial connective tissues (connective tissue under the epithelia- brings nutrients)

Tunica media  

Smooth muscle fibre (allow constriction and dilation) in loose connective tissue (loose areolar) May contain elastic fibres (some blood vessels)

Tunica externa/ adventia   

Connective tissues Merges with surrounding connective tissue May contain vaso vasorum (in some blood vessels- very big ones the adventia contains vaso vasorum- this means there’ll be blood vessels within blood vessels e.g. large blood vessels like the aorta will need blood supply within its walls. The blood will be running in the connective tissue on the outside)

ARTERIES VS VEINS         

Arteries takes blood to organs Veins take blood away (containing waste products) from organs to the heart Arteries have thicker walls and lumen appears to be smaller compare to veins Veins lumen is distorted (not circular) Artery lumen is somewhat round Artery maintains its shape Arteries also have a smaller lumen compare to veins- this narrow lumen is there to increase pressure Arteries are more resilient than veins (if compressed it’ll go back to its original shape but if you compressed veins they’ll flatten) Arteries do not contain valves whereas veins contain many valves

ARTERIES      

Blood under high pressure When heart contracts the pressure in the artery can go up to 120-130 mm Mercury When the heart relaxes it can go to 60 mm mercury When someone has high blood pressure the pressure in the artery can go up to 180-190 mm mercury (which is very high Have thick wall (due to high pressure – to withstand high pressure) Resemble garden hoses

VEINS   

Blood under low pressure Therefore, have thin walls due to low pressure Resemble fire hoses

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May have valves to prevent back flow- this is due to the low pressure

TYPES OF ARTERIES 1. Elastic (also called conducting arteries- conduct blood from heart) 2. Muscular (also called distributing arteries- distributes blood to different organs) 3. Arterioles (also called resistance vessels because can constrict to restrict blood flow) ELASTIC (CONDUCTING) ARTERIES       

Conducting arteries are the big arteries E.g. aorta, brachiocephalic & common carotid Aorta can have a Diameter: up to 2.5cm These big arteries must withstand changes in pressure during the cardiac cycle and ensure continuous blood flow even in low pressure Structural adaptations- tunica media is very thick and has many elastic fibres and few smooth muscle cells When the heart contracts and blood is forced into the aorta, the aorta will expand and stretch when the heart relaxes, we get an elastic recoil of the aortas wall. This recoil will cause blood to continue to flow onwards This is all due to the structural adaptations of the tunica media

MUSCULAR (DISTRIBUTING) ARTERIES        

Most named arteries e.g. brachial & femoral Muscular arteries are much small in diameter (0.5mm-0.4cm) than elastic arteries Distributes blood to muscles and organs Capable of vasodilation and vasoconstriction in order to control the rate of blood flow to suit the needs of the organ Structural adaptations- in the tunica media we have manly smooth muscle cells +++ in tunica media - distinct internal (IEL) & external (EEL) elastic laminae Between media and intima, we get an internal elastic laminae Between media and externa, we get an external elastic laminae The adventia (externa) on the outside is very thick this is because the blood vessels are going through between lots of different organs, so we have a thick that’ll merge with surrounding vessels

ARTERIOLES (RESISTANCE VESSELS)      

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Capable of vasoconstriction and vasodilation Involved in blood pressure control Control blood flow to organs Involved in blood pressure control Smaller in diameter: less or equal to 30 micrometres Structural adaptations: made up of a tunica intima and about two – three layers of smooth muscle on the outside- this smooth muscle can do the constriction and dilation (tunica media) The tunica adventia (also called externa) is poorly define because it merges with surrounding tissues

CAPILLARIES

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Arterioles will lead to capillaries Connect arterioles and venules (microcirculation) Site of gaseous exchange Thin walls facilitate diffusion Blood flow through capillaries is slow- because we want nutrients and gases to be able to have time to pass through the wall Walls of capillaries will allow a two-way exchange (Structure permits 2-way exchange) 89 micrometres in diameter Found near almost every cell Single layer of epithelium (or endothelium) with under lined basement membrane

DIFFERENT TYPES OF CAPILLARIES: Continuous   

Most parts of the body have continuous capillaries E.g. Skeletal and smooth muscle, CT (connective tissue) and lungs These capillaries are complete. E.g. one epithelia cell will be connected to another epithelial cell. There are no gaps between the epithelial cells. Anything that crosses from the lumen outside must pass through the cell wall

Fenestrated    

Fenestrated- made of simple layer epithelium with a basement membrane Between some cells we have little pores penetrating the endothelial lining Rapid exchange of water or large solutes (e.g. small peptides) in some areas Fenestrated capillaries are mostly there for Absorption e.g. in the kidneys, choroid plexus and endocrine glands

SINUSOIDAL        

least seen walls have lots of gaps in them in the continuous we have no gaps, in fenestrated we have little pores and in sinusoidal we have big gaps spaces between endothelial cells Incomplete or absent basement membrane (BM)- purpose of this is so larger solutes can get across Exchange of large solutes i.e. plasma proteins Specialised lining cells (e.g. in the liver, phagocytic cells engulf damaged RBCs) Blood moves slowly through sinusoidal

CAPILLARY BEDS: 

Capillary beds are formed of many capillaries interconnecting with each other

Metarterioles:    

A metarteriole supplies a single capillary bed Coming off the metarterioles are many capillaries Each metarteriole continues as a thoroughfare channel which leads directly to a vein and has numerous capillaries leading off it If we constrict the opening of a metarteriole it can reduce flow to a whole capillary bed

PRECAPILLARY SPHINCTER:     

Each capillary has its own precapillary sphincter Guard the entrance to each capillary You can constrict a capillary to stop/reduce flow to a certain area- Contraction narrow entrance You can dilate a capillary to allow/ increase flow to a certain area- relaxation dilates entrance Precapillary sphincters can be selective which capillary gets blood

ARTERIOVENOUS ANASTOMOSES:  

Form direct communication between arteriole and venule When dilated blood bypasses the capillary bed and flows directly to venous circulation- this is much quicker

VENULES:   

 

Collect blood from capillary bed and deliver it to the small veins Venules are about diameter: average 20 micrometre (varies) Structural adaptations – they’re small we just have an endothelium on a basement membrane. As the venules get bigger, we start to get more and more layers of smooth muscles around them Small- endothelium on a basement membrane Larger- increasing numbers of smooth muscle cells located outside endothelium

VEINS (called also CAPACITANCE VESSELS):       

Veins are classified according to size Small less than 2 mm in diameter Medium 2-9mm in diameter Large more than 9mm in diameter e.g. superior and inferior vena cava Pressure in veins is always low- Low pressure system Easily distensible (capacitance)- when they distend, they can hold more blood Structural adaptations- walls are thins and they have a predominant/large tunica externa and have valves to aid blood flow due to the fact many of the veins are taking blood against gravity and low blood pressure

VALVES & MUSCULOVENOUS PUMP:   

Musculovenous pump helps blood come back to the heart Muscles around veins force on the vein which forces blood up Very important in making sure blood gets back to the heart

PRESSURE CHANGES     

Heart contracts = systole Heart relaxes = diastole In the arteries and down to the arterioles we have pressures changes When the heart contracts it’s about 120mm mercury

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When it relaxes its about 80mm mercury The change in pressure is why we need adapted blood vessels that can withstand the changes Highest pressure in aorta Blood pressure starts to drop in capillaries and venules and pressure remains quite constant

DISTRINUTION OF BLOOD:  

At rest 65-70% of our blood is in our veins 30-35% is spread along the lungs

ANATOMICAL TERMINOLOGY: Define the terms:            

Anatomical position Anterior(ventral)- towards front Posterior(dorsal)- towards back Superior- towards ceiling Inferior- towards ground Medial- towards middle Lateral- away from middle (thumb is lateral to the little finger) Proximal- closer to Distal – further away Coronal? Frontal plane Horizontal/ transverse plane Sagittal plane

THE ANATOMICAL POSITION:   

Looking at diagrams in book look at their right and left side not yours Arm is from shoulder to elbow Forearm is from elbow to hand (upper limb)

ANATOMICAL PLANE:   

Coronal plane - Passes from side to side slitting body into front and back Transverse plane- splits the body into upper and lower parts Sagittal plane- passes from front to back splitting body into right and left sides...