blood vessels part 1. blood vessels 3 major types of blood vessels: arteries – carries blood away...
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Blood VesselsPART 1
Blood Vessels 3 major types of blood vessels:
Arteries – carries blood away from the heart
Capillaries – The functional vessels which actually delivers nutrients to cells
Veins – return blood to the heart
Structure of Blood Vessels Composed of three layers (tunics)
Tunica intima – composed of simple squamous epithelium
Tunica media – sheets of smooth muscle Contraction – vasoconstriction Relaxation – vasodilation
Tunica externa – composed of connective tissue
Lumen Central blood-filled space of a vessel
Generalized structure of arteries, veins, and capillaries.
Artery VeinTunica intima
Tunica media(smooth muscle andelastic fibers)
Tunica externa(collagen fibers)
Capillary
Lumen
Endothelial cells
Basement membrane
Lumen
Capillary network
Valve
Vasa vasorum
External elastic membrane
Internal elastic membraneSubendothelial layer
Endothelium
Structure of Arteries, Veins, and Capillaries
Figure 19.1a
Types of Arteries Elastic arteries – the largest arteries
Diameters range from 2.5 cm to 1 cm Includes the aorta and its major branches Sometimes called conducting arteries High elastin content dampens surge of blood
pressure
Figure 19.2a
Types of Arteries
Muscular (distributing) arteries Lie distal to elastic
arteries Diameters range from 1
cm to 0.3 mm Includes most named
arteries Tunica media is thick Unique features
Internal and external elastic laminae
Figure 19.2b
Figure 19.2c
Types of Arteries Arterioles
Smallest arteries Diameters range from 0.3 mm to 10 µm Larger arterioles possess all three tunics Diameter of arterioles controlled by
Local factors in the tissues Sympathetic nervous system
Capillaries Smallest blood vessels
Diameter from 8–10 µm Red blood cells pass through single file Types of Capillaries:
Continuous – most common – diffusion and intercellular clefts for larger molecules
Fenestrated – “windows” has holes – found in kidneys, intestines and endocrine glands
Sinusoids – wide, leaky capillaries. Follows a twisted path and has wide and narrow areas. Useful when exchange of large materials is necessary such as in the bone marrow and spleen
RBCs in a Capillary
Figure 19.3
Capillary Beds Network of capillaries running
through tissues Precapillary sphincters
Regulate the flow of blood to tissues Tendons and ligaments – poorly
vascularized Epithelia and cartilage – avascular
Receive nutrients from nearby CT
Capillary Beds
Figure 19.4a
Capillary Beds
Figure 19.4b
Capillary Permeabillity Endothelial cells – held together by tight
junctions and desmosomes 4 Routes of molecules:
1. Direct Diffusion through endothelial membrane 2. Intercellular clefts – unjoined areas of cell membrane
to allow passage of large molecules 3. Pinocytotic vesicles – vesicles invaginate from the
plasma membrane and migrate across the endothelial cell transporting dissolved gasses, nutrients and wast products
4. fenestrations – pores in the endothelial cells allow passage of many small molecules
Structure of Capillaries – Cross Section
Figure 19.5a
A vesicle within an endothelial cell to transport liquid from blood to tissues
Structure of Capillaries – Cross Section
Figure 19.5b
In kidneys
Routes of Capillary Permeability
Four routes into and out of capillaries Direct diffusion – across capillary wall
(endothelial cell membrane)
Through intercellular clefts – most Through cytoplasmic vesicles Through fenestrations - kidneys
Low Permeability Capillaries Blood-brain barrier
Capillaries have complete tight junctions
No intercellular clefts are present Vital molecules pass through
Highly selective transport mechanisms Not a barrier against
Oxygen, carbon dioxide, and some anesthetics
Sinusoids Wide, leaky capillaries found in
some organs Usually fenestrated Intercellular clefts are wide open
Occur in bone marrow and spleen Sinusoids have a large diameter and
twisted course
Sinusoids
Figure 19.5c
Veins Conduct blood from capillaries toward the heart Blood pressure is much lower than in arteries Smallest veins – called venules
Diameters from 8 – 100 µm Smallest venules – called postcapillary
venules Venules join to form veins
Tunica externa is the thickest tunic in veins
Figure 19.6
Mechanisms to Counteract Low Venous Pressure
Valves in some veins Particularly in
limbs Skeletal muscle
pump Muscles press
against thin-walled veins
Vascular Anastomoses Vessels interconnect to form vascular
anastomoses Organs receive blood from more than one
arterial source Neighboring arteries form arterial
anastomoses Provide collateral channels
Veins anastomose more frequently than arteries
Vasa Vasorum Tunica externa of large vessels have
Tiny arteries, capillaries, and veins Vasa vasorum vessels of vessels
Nourish outer region of large vessels such as the aorta, brachiocephalic a., common iliac a.
Inner half of large vessels receive nutrients from luminal blood
It’s how the cells of the large vessels receive nutrients
Pulmonary Circulation Pulmonary trunk leaves the right
ventricle Divides into right and left pulmonary
arteries Superior and inferior pulmonary
veins Carry oxygenated blood into the left
atrium
Pulmonary Circulation
Figure 19.7
Systemic Circulation Systemic Arteries
Carry oxygenated blood away from the heart
Aorta – largest artery in the body
Major Arteries
Figure 19.8a
The Aorta Ascending aorta – arises from the left
ventricle Branches – coronary arteries
Aortic arch – lies posterior to the manubrium Branches
Brachiocephalic trunk Left common carotid Left subclavian arteries
The Aorta
Figure 19.9
The Aorta Descending aorta – continues from
the aortic arch Thoracic aorta – in the region of T5–T12
Abdominal aorta – ends at L4
Divides into right and left common iliac arteries
Arteries of the Head and Neck
Figure 19.10a
Figure 19.10c
Major Arteries Serving the Brain Cerebral arterial circle – Circle of Willis
Arteries of the Upper Limb and Thorax
Figure 19.11
Arteries of the Abdominal Aorta Inferior phrenic arteries Celiac trunk Superior mesenteric artery Suprarenal arteries Renal arteries Gonadal (testicular or ovarian) arteries Inferior mesenteric artery Common iliac arteries
Arteries of the Abdominal Aorta
Figure 19.12
The Celiac Trunk and Main Branches
Figure 19.13
Figure 19.14
Distribution of the Superior and Inferior Mesenteric Arteries
Arteries of the Pelvis and Lower Limbs
Internal iliac arteries External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery
Internal Iliac Artery
Figure 19.15b
Arteries of the Pelvis and Lower Limbs
Figure 19.16a
Arteries of the Pelvis and Lower Limbs
Figure 19.16b
Figure 19.17
Systemic Veins Three major veins enter the right
atrium Superficial veins lie just beneath the
skin Multivein bundles – venous plexuses Unusual patterns of venous drainage
Dural sinuses Hepatic portal system
Venae Cavae and Tributaries Superior vena cava
Returns blood from body regions superior to the diaphragm
Inferior vena cava Returns blood from body regions
inferior to the diaphragm Superior and inferior vena cava
Join the right atrium
Abdominal Cavity Showing Vasculature
Figure 19.19
Major Veins of the Systemic Circulation
Figure 19.18
Figure 19.20b
Veins of the Head and Neck Dural Sinuses
Superior and inferior sagittal sinuses
Straight sinus Transverse
sinuses Sigmoid sinus
Figure 19.20a
Veins of the Head and Neck
Venous drainage Internal jugular veins External jugular veins Vertebral veins
Veins of the Upper Limbs Deep Veins
Follow the paths of companion arteries Have the same names as the companion
arteries Superficial veins
Visible beneath the skin Cephalic vein Basilic vein Median cubital vein Median vein of the forearm
Figure 19.21a
Antecubital Fossa Form
anastomese frequently
Median cubital vein is used to obtain blood or administer IV fluids
Figure 19.22
Figure 19.21b
Veins of the Thorax Azygos vein Hemiazygos vein Accessory
hemiazygos vein
Veins of the Abdomen Lumbar veins Gonadal (testicular or ovarian) veins Renal veins Suprarenal veins Hepatic veins
Tributaries of the Inferior Vena Cava
Figure 19.23
The Hepatic Portal System A specialized part of the vascular
circuit Picks up digested nutrients Delivers nutrients to the liver for
processing
The Basic Scheme of the Hepatic Portal System
Figure 19.24
Veins of the Hepatic Portal System
Figure 19.25
Veins of the Pelvis and Lower Limbs
Deep veins Share the name of the accompanying
artery Superficial veins
Great saphenous vein empties into the femoral vein
Small saphenous vein empties into the popliteal vein
Veins of the Right Lower Limb and Pelvis
Figure 19.26a
Figure 19.26b
Figure 19.27
Disorders of the Blood Vessels Aneurysm – a ballooning out of a major artery such as the aorta Deep vein thrombosis of the lower limb – formation of clots in the veins of the leg or
thigh. The clot may detach and travel to the heart and pulmonary trunk, blocking a branch of the pulmonary artery which may be fatal
Venous disease – inadequate drainage of venous blood from the limb. Tissues become ischemic and vulnerable to damage and ulceration. Caused by the failure of valves so blood pools and causes swelling of legs.
Arteriovenous malformation – a congenital condition in which capillaries fail to develop in a certain location so that an artery continues directly into a vein. The high pressure entering a vein cause an aneurysm which can compress nearby tissues or burst and cause a stroke. Normally occurs in the brain
Atherosclerosis – arterial walls become thick and stiff from hypertension, chemicals or viral or bacterial infections. Irritation of the endothelium prompts inflammatory response. LDL is attracted, cholesterol follows.
Microangiopathy of diabetes – complication of diabetes. Elevated blood sugar lead to deposit of glycoproteins in the basement membrane of capillaries diminishing the efficiency of the capillary. Organs most vulnerable are: kidneys, retina, periheral nerves and feet.
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