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Blood Vessels PART 1
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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
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Structure of Arteries, Veins, and Capillaries
Figure 19.1a
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Types of Blood Vessels Arteries – carry blood away from the heart
Capillaries – smallest blood vessels The site of exchange of molecules between blood and tissue fluid Veins – carry blood toward the heart
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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
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Unique features 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
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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 Figure 19.2c
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Capillaries Smallest blood vessels Diameter from 8–10 µm
Red blood cells pass through single file Site-specific functions of capillaries Lungs – oxygen enters blood, carbon dioxide leaves Small intestines – receive digested nutrients Endocrine glands – pick up hormones Kidneys – removal of nitrogenous wastes
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RBCs in a Capillary Figure 19.3
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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 PLAY Anatomy Review: Blood Vessel Structure and Function
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Capillary Beds Figure 19.4a
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Capillary Beds Figure 19.4b
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Capillary Permeabillity
Endothelial cells – held together by tight junctions and desmosomes Intercellular clefts – gaps of unjoined membrane Small molecules can enter and exit Two types of capillary Continuous – most common Fenestrated – have pores
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Structure of Capillaries – Cross Section
Figure 19.5a
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Structure of Capillaries – Cross Section
Figure 19.5b
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Routes of Capillary Permeability
Four routes into and out of capillaries Direct diffusion – across capillary wall Through intercellular clefts – most Through cytoplasmic vesicles Through fenestrations - kidneys
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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
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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
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Sinusoids Figure 19.5c
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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
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Mechanisms to Counteract Low Venous Pressure
Valves in some veins Particularly in limbs Skeletal muscle pump Muscles press against thin-walled veins Figure 19.6
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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
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Vasa Vasorum Tunica externa of large vessels have
Tiny arteries, capillaries, and veins Vasa vasorum vessels of vessels Nourish outer region of large vessels Inner half of large vessels receive nutrients from luminal blood
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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
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Pulmonary Circulation
Figure 19.7
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Systemic Circulation Systemic Arteries
Carry oxygenated blood away from the heart Aorta – largest artery in the body
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Major Arteries Figure 19.8a
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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
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The Aorta Figure 19.9
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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
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Arteries of the Head and Neck
Figure 19.10a
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Major Arteries Serving the Brain
Cerebral arterial circle Figure 19.10c
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Arteries of the Upper Limb and Thorax
Figure 19.11
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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
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Arteries of the Abdominal Aorta
Figure 19.12
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The Celiac Trunk and Main Branches
Figure 19.13
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Distribution of the Superior and Inferior Mesenteric Arteries
Figure 19.14
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Arteries of the Pelvis and Lower Limbs
Internal iliac arteries External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery
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Internal Iliac Artery Figure 19.15b
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Arteries of the Pelvis and Lower Limbs
Figure 19.16a
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Arteries of the Pelvis and Lower Limbs
Figure 19.16b
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Figure 19.17
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Fenestrated Capillary
Describe relevance of pulse points to clinical anatomy Figure 19.5b
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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
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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
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Abdominal Cavity Showing Vasculature
Figure 19.19
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Major Veins of the Systemic Circulation
Figure 19.18
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Veins of the Head and Neck
Dural Sinuses Superior and inferior sagittal sinuses Straight sinus Transverse sinuses Sigmoid sinus Figure 19.20b
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Veins of the Head and Neck
Venous drainage Internal jugular veins External jugular veins Vertebral veins Figure 19.20a
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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
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Figure 19.21a
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Antecubital Fossa Form anastomese frequently
Median cubital vein is used to obtain blood or administer IV fluids Figure 19.22
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Veins of the Thorax Azygos vein Hemiazygos vein
Accessory hemiazygos vein Figure 19.21b
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Veins of the Abdomen Lumbar veins
Gonadal (testicular or ovarian) veins Renal veins Suprarenal veins Hepatic veins
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Tributaries of the Inferior Vena Cava
Figure 19.23
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The Hepatic Portal System
A specialized part of the vascular circuit Picks up digested nutrients Delivers nutrients to the liver for processing
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The Basic Scheme of the Hepatic Portal System
Figure 19.24
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Veins of the Hepatic Portal System
Figure 19.25
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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
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Veins of the Right Lower Limb and Pelvis
Figure 19.26a
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Figure 19.26b
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Figure 19.27
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Disorders of the Blood Vessels
Aneurysm Deep vein thrombosis of the lower limb Venous disease Microangiopathy of diabetes Arteriovenous malformation
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Blood Vessels Throughout Life
Fetal Circulation All major vessels in place by month three of development Differences between fetal and postnatal circulation Fetus must supply blood to the placenta Very little blood is sent through the pulmonary circuit
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Vessels to and from the Placenta
Umbilical vessels run in the umbilical cord Paired umbilical arteries Unpaired umbilical vein Fetal vessels and structures Ductus venosus Ligamentum teres Ligamentum venosum Medial umbilical ligaments
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Shunts Away from the Pulmonary Circuit
Foramen ovale Ductus arteriosus
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Fetal and Newborn Circulation Compared For your information only!
Figure 19.28a
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Fetal and Newborn Circulation Compared For your information only!
Figure 19.28b
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Blood Vessels in Adulthood
Atherosclerosis begins in youth Consequences evident in middle to old age Males More atherosclerosis than females between ages 45 – 65 Females Experience heart disease and atherosclerosis later in life
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