Circulatory System: Blood Vessels Exercise 32. Structure of Artery and Vein.
Blood vessels - general structure
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Transcript of Blood vessels - general structure
Blood vessels - general structure
• Three major types of blood vessels are : arteries, capillaries and veins
• The walls of all blood vessles except capillaries are composed of three distinct layers (tunics) surrounding a space (lumen).
• The tunics are from inside to outside – Tunic intima - endothelium, simple squamous epithelium
– Tunica media - circulary arranged smooth muscle and elastic fibers interspersed with sheets of elastin
– Tunica adventitia - collagen
Arteries
• Elastic arteries - conducting arteries– arterial pulse
• Muscular arteries - distributing arteries
• Arterioles
Capillaries
• Continous capillaries
• Fenestrated capillaries
• Sinusoids
Capillary Beds
• General structure - terminal arteriole ---------> metarteriole -------------> thoroughfare channel -----------------> postcapillary venule (PICTURE)
• Vascular shunts
• True capillaries
Veins
• Venules
• Veins
• Venous sinuses
Cardiac Output
CO = SV x HR
SV = EDS - ESV
• Therefore to regulate CO we can alter HR or SV– SV can be altered by alteruing either EDS or ESV
Regulation of SV
• Preload - Starling Law of the Heart
• Contractility
• Afterload
Regulation of HR
• Neuronal - sympathetic and parasympathetic (vagal)
• Chemical– Hormones
– ions
• Other factors
Definition of variables
• Blood pressure- P =F/A the force exerted on wall of blood vessel per unit area
• Resistance - the opposition to flow mainly in the periphery PR or TPR
• Blood viscosity - opposition to flow related to the thickness of blood
• Total BV length
• Total BV diameter
Relationships among the variables
• BP = CO X TPR
• Resistance
– directly proportional to BV L
– directly proportional to 1/r4
– Directly proportional to blood viscocity
• BF = difference in BP in different parts of the vascular system / TPR
Relationships among the variables
• MAP = dBP + 1/3 pulse pressure– pulse pressure = SBP - DBP
• BP and BF velocity in different parts of vascular system
Control of BP
• A Short term -
1 neural controls
• Cardiovascular center
• baroreceptor initiated reflexes
• chemoreceoptor initiated reflexes
• higher brain involvement
Control of BP • 2 Hormones• adrenal medulla hormones
• ANF atrail natriuretic factor
• ADH antidiuretic hormone
• Angiotensin II
• EDF endothelium derived factors
• NO nitric oxide also called endothelium derived relaxing factor EDRF
Control of BP
• 3 Drugs and chemicals• alcohol
• inflammatory chemicals -histamine , kinins
Control of BP
• B Long term -
1. kidney regulation
Capillary filtration