Sonya Schuh-Huerta, Ph.D. The Blood Vessels ~The Vascular System Ch 20 Human Anatomy Sonya Schuh-Huerta, Ph.D. Leonardo Da Vinci

Types of Blood Vessels Arteries  carry blood Away from the heart Capillaries  smallest blood vessels The site of exchange of molecules between blood & tissue fluid Veins  carry blood toward the heart

Structure of Blood Vessels Composed of 3 layers (= tunics) Tunica intima  endothelium; composed of simple squamous epithelium Tunica media  sheets of smooth muscle Contraction = vasoconstriction Relaxation = vasodilation Tunica externa  composed of C.T. Lumen Central blood-filled space of a vessel

Structure of Blood Vessels Tunica media (smooth muscle and elastic fibers) Tunica externa (collagen fibers) Artery Vein Lumen Internal elastic membrane External elastic membrane Valve (b) Endothelial cells Basement membrane Capillary network Tunica intima Subendothelial layer Endothelium

Structure of Arteries, Veins, & Capillaries Artery (a)

Structure of Arteries, Veins, & Capillaries Lab iScopy Pix

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 BP Vasa vasorum Elastin Lumen Tunica externa media intima (a) Elastic artery (aorta, 12)

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 feature Internal & external elastic laminae External elastic membrane Internal elastic membrane Lumen Tunica externa Tunica media (b) Muscular artery (40)

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 Lumen Endothelium Tunica media (c) Small arteriole (285)

Capillaries Smallest blood vessels Diameter from 8–10 µm RBCs 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/release hormones Kidneys  removal of nitrogenous wastes

RBCs in a Capillary – Single File

Capillary Beds Network of capillaries running through tissues Precapillary sphincters Regulate the flow of blood to tissues Tendons & ligaments  poorly vascularized Epithelia & cartilage  avascular Receive nutrients from nearby CT

Capillary Beds Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open—blood flows through true capillaries.

Capillary Beds Terminal arteriole Postcapillary venule (b) Sphincters closed—blood flows through metarteriole—thoroughfare channel & bypasses true capillaries (no blood/O2 to tissue)

Capillary Permeability Endothelial cells  held together by tight junctions & desmosomes Intercellular clefts  gaps of unjoined membrane Small molecules can enter & exit 2 types of capillary Continuous  most common Fenestrated  have pores; least common

Continuous Capillary Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Basement membrane Tight junction Pinocytotic vesicles Endothelial nucleus (a) Continuous capillary. Least permeable and most common (e.g., skin, muscle).

Fenestrated Capillary Pinocytotic vesicles Red blood cell in lumen Fenestrations (pores) Endothelial nucleus Intercellular cleft Basement membrane Tight junction Endothelial cell (b) Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in special locations (e.g., kidney, small intestine).

Routes of Capillary Permeability 4 routes into & out of capillaries Direct diffusion Through intercellular clefts Through cytoplasmic vesicles Through fenestrations (= pores)

Low Permeability Capillaries Blood-Brain Barrier Capillaries have complete tight junctions No intercellular clefts present Vital molecules pass through Highly selective transport mechanisms Not a barrier against: Oxygen, carbon dioxide, & some anesthetics (ie. many drugs)

Sinusoids Wide, leaky capillaries found in some organs Usually fenestrated Intercellular clefts are wide open Occur in bone marrow, spleen, & liver Sinusoids have large diameter & twisted course

Sinusoids Endothelial cell Red blood cell in lumen Large intercellular cleft Tight junction Incomplete basement membrane Nucleus of endothelial cell (c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen).

Veins Conduct blood from capillaries toward the heart Blood pressure is much lower than in arteries Smallest veins  called venules Diameters from 8–100 m Smallest venules  called postcapillary venules Venules join to form veins Tunica externa is the thickest tunic in veins (not the tunica media)

Mechanisms to Counteract Low Venous Pressure Valve (open) Contracted skeletal muscle Valve (closed) Vein Direction of blood flow Valves in some veins! Particularly in limbs Skeletal muscle pump Muscles press against thin-walled veins Helps return blood to heart & prevent pooling

Summary of Blood Vessel Anatomy

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, & veins Vasa vasorum  “vessels of vessels” Nourish outer region of large vessels Inner half of large vessels receive nutrients from luminal blood

Pulmonary Circulation Pulmonary trunk leaves the right ventricle Divides into right & left pulmonary arteries Superior & inferior pulmonary veins Carry oxygenated blood into the left atrium

Pulmonary Circulation Left pulmonary artery Air-filled alveolus of lung Aortic arch Pulmonary trunk Right pulmonary artery O2 Three lobar arteries to right lung CO2 Pulmonary capillary Gas exchange Two lobar arteries to left lung Pulmonary veins Pulmonary veins Right atrium Left atrium Right ventricle Left ventricle

Blood Vessels Throughout Life Fetal circulation All major vessels in place by month 3 of development Differences between fetal & postnatal circulation Fetus must supply blood to the placenta Very little blood is sent through the pulmonary circuit (lungs not doing gas exchange yet; no breathing until born)

Shunts Away from the Pulmonary Circuit Foramen ovale Ductus arteriosus

Vessels to & from the Placenta Umbilical vessels run in the umbilical cord Paired umbilical arteries Unpaired umbilical vein Fetal vessels & structures Ductus venosus Ligamentum teres Ligamentum venosum

Fetal & Newborn Circulation Compared Fetus Aortic arch Superior vena cava Ductus arteriosus Ligamentum arteriosum Pulmonary artery Pulmonary veins Heart Lung Foramen ovale Fossa ovalis Liver Ductus venosus Ligamentum venosum Hepatic portal vein Umbilical vein Ligamentum teres Inferior vena cava Umbilicus Abdominal aorta Common iliac artery Umbilical arteries Medial umbilical ligaments Urinary bladder Umbilical cord High oxygenation Moderate oxygenation Placenta Low oxygenation Very low oxygenation (a)

Disorders of the Blood Vessels Aneurysm Deep vein thrombosis of the lower limb Venous disease Microangiopathy of diabetes Arteriovenous malformation Varicose veins 

Abdominal Aneurysm Aortic aneurysm

Disorders of the Blood Vessels Atherosclerosis begins in youth Often related to fatty diet, little exercise, etc. Consequences evident in middle – old age Males (ages 45–65) More common than in females Females Experience heart disease & atherosclerosis later in life than males

Atherosclerosis

What is one of the best ways to maintain vascular health…?

Lab Guide to the Vessels

Systemic Circulation Systemic arteries Carry oxygenated blood away from the heart Aorta  largest artery in the body!!!

Major Arteries Arteries of the head and trunk Internal carotid artery External carotid artery Arteries that supply the upper limb Common carotid arteries Vertebral artery Subclavian artery Subclavian artery Brachiocephalic trunk Axillary artery Aortic arch Ascending aorta Coronary artery Brachial artery Thoracic aorta (above diaphragm) Celiac trunk Radial artery Abdominal aorta Ulnar artery Superior mesenteric artery Renal artery Deep palmar arch Gonadal artery Inferior mesenteric artery Superficial palmar arch Common iliac artery Digital arteries Internal iliac artery Arteries that supply the lower limb External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery Arcuate artery (a) Anterior view

Major Arteries – Pulse Points Superficial temporal artery Facial artery Common carotid artery Brachial artery Radial artery Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery

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 Left internal jugular vein Right common carotid artery Left subclavian artery Right subclavian artery Right internal jugular vein Left subclavian vein Right subclavian vein Left brachiocephalic vein Right brachiocephalic vein Left common carotid artery Brachiocephalic trunk Aortic arch Left pulmonary artery Right pulmonary artery Ligamentum arteriosum Superior vena cava Thoracic aorta Ascending aorta Pulmonary trunk Right atrium Left atrium Left ventricle Right ventricle Inferior vena cava

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 & left common iliac arteries

Common Carotid Arteries Located in the anterior triangle of the neck 2 branches of the common carotid artery: External carotid artery Internal carotid artery

Common Carotid Arteries External carotid artery branches: Superior thyroid artery Lingual artery Facial artery Occipital artery Posterior auricular artery Superficial temporal artery Maxillary artery

Common Carotid Arteries Internal carotid artery branches: Optithalmic artery Anterior cerebral artery Anterior communicating artery Forms part of the cerebral arterial circle Middle cerebral artery

Arteries of the Head & Neck Superficial temporal artery Ophthalmic artery Maxillary artery Occipital artery Facial artery Lingual artery Superior thyroid artery Larynx Thyroid gland (overlying trachea) Clavicle (cut) Brachiocephalic trunk Internal thoracic Basilar artery Vertebral artery Internal carotid artery Subclavian Axillary (a) Arteries of the head and neck, right aspect External Common Thyrocervical Costocervical Branches of the external

Vertebral Arteries Supply the posterior brain Join to form the basilar artery Basilar artery divides into 2 posterior cerebral arteries Posterior cerebral arteries connect to the posterior communicating arteries

Cerebral Arterial Circle 2 posterior communicating arteries join the anterior communicating artery Anterior Frontal lobe Cerebral arterial circle (circle of Willis) Optic chiasma Anterior communicating artery Middle cerebral artery Anterior cerebral artery Internal carotid artery Posterior communicating artery Mammillary body Posterior cerebral artery Temporal lobe Basilar artery Vertebral artery Pons Occipital lobe Cerebellum Posterior (c) Major arteries serving the brain (inferior view, right side of cerebellum and part of right temporal lobe removed)

Arteries of the Upper Limb Subclavian artery enters the axilla as the axillary artery Axillary artery becomes the brachial artery at the inferior border of teres major Brachial artery divides into  Radial artery & ulnar artery

Arteries of the Upper Limb & Thorax Vertebral artery Common carotid arteries Thyrocervical trunk Right subclavian artery Costocervical trunk Suprascapular artery Left subclavian artery Thoracoacromial artery Brachiocephalic trunk Axillary artery Posterior intercostal arteries Subscapular artery Anterior intercostal artery Posterior circumflex humeral artery Internal thoracic artery Anterior circumflex humeral artery Lateral thoracic artery Brachial artery Descending aorta Deep artery of arm Common interosseous artery Radial artery Ulnar artery Deep palmar arch Superficial palmar arch Digital arteries

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 Hiatus (opening) for inferior vena cava Diaphragm Inferior phrenic artery Hiatus (opening) for esophagus Middle suprarenal artery Adrenal (suprarenal) gland Renal artery Celiac trunk Superior mesenteric artery Kidney Abdominal aorta Gonadal (testicular or ovarian) artery Lumbar arteries Ureter Inferior mesenteric artery Median sacral artery Common iliac artery

The Celiac Trunk & Main Branches Liver (cut) Diaphragm Inferior vena cava Esophagus Celiac trunk Common hepatic artery Left gastric artery Hepatic artery proper Stomach Gastroduodenal artery Splenic artery Left gastroepiploic artery Right gastric artery Gallbladder Spleen Pancreas (major portion lies posterior to stomach) Right gastroepiploic artery Duodenum Abdominal aorta Superior mesenteric artery (a) The celiac trunk and its major branches. The left half of the liver has been removed.

Arteries of Pelvis & Lower Limbs Internal iliac arteries External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery

Arteries of the Pelvis Aorta Common iliac artery Internal iliac artery External iliac artery (a) Anterior view

Arteries of the Pelvis & Lower Limbs Common iliac artery Internal iliac artery Superior gluteal artery External iliac artery Deep artery of thigh Lateral circumflex femoral artery Descending branch Medial circumflex femoral artery Obturator artery Femoral artery Adductor hiatus Popliteal artery Genicular artery Anterior tibial artery Posterior tibial artery Fibular artery Dorsalis pedis artery Arcuate artery Dorsal metatarsal arteries (a) Anterior view

Arteries of the Pelvis & Lower Limbs Popliteal artery Anterior tibial artery Posterior tibial artery Fibular artery Dorsalis pedis artery (from top of foot) Lateral plantar artery Medial plantar artery Plantar arch (b) Posterior view of leg

Systemic Veins 3 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 & 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

Major Veins of the Systemic Circulation Veins of the head and trunk Dural venous sinuses Veins that drain the upper limb External jugular vein Vertebral vein Subclavian vein Axillary vein Internal jugular vein Cephalic vein Right and left brachiocephalic veins Brachial vein Basilic vein Superior vena cava Median cubital vein Great cardiac vein Ulnar vein Hepatic veins Radial vein Splenic vein Digital veins Hepatic portal vein Renal vein Veins that drain the lower limb Superior mesenteric vein External iliac vein Inferior mesenteric vein Femoral vein Inferior vena cava Great saphenous vein Popliteal vein Common iliac vein Posterior tibial vein Internal iliac vein Anterior tibial vein Small saphenous vein Dorsal venous arch Dorsal metatarsal veins

Veins of the Head & Neck Venous drainage Internal jugular veins External jugular veins Vertebral veins Ophthalmic vein Superficial temporal vein Facial vein Occipital vein Posterior auricular vein External jugular vein Vertebral vein Internal jugular vein Superior and middle thyroid veins Brachiocephalic vein Subclavian vein Superior vena cava (a) Veins of the head and neck, right superficial aspect

Veins of the Head & Neck Dural sinuses Superior & inferior sagittal sinuses Straight sinus Transverse sinuses Sigmoid sinus Superior sagittal sinus Falx cerebri Inferior sagittal sinus Straight sinus Cavernous sinus Confluence of sinuses Transverse sinuses Sigmoid sinus Jugular foramen Right internal jugular vein (b) Dural venous sinuses of the brain

Veins of the Thorax Azygos vein Hemiazygos vein Accessory hemiazygos vein

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

Veins of the Thorax & Right Upper Limb Brachiocephalic veins Internal jugular vein Right subclavian vein External jugular vein Axillary vein Left subclavian vein Brachial vein Superior vena cava Cephalic vein Azygos vein Basilic vein Accessory hemiazygos vein Hemiazygos vein Posterior intercostals Inferior vena cava Median cubital vein Ascending lumbar vein Median antebrachial vein Basilic vein Cephalic vein Ulnar vein Radial vein Deep palmar venous arch Superficial palmar venous arch Digital veins

Veins of the Abdomen Lumbar veins Gonadal (testicular or ovarian) veins Renal veins Suprarenal veins Hepatic veins

Tributaries of the Inferior Vena Cava Inferior phrenic vein Hepatic veins Left suprarenal vein Inferior vena cava Renal veins Right suprarenal vein Left ascending lumbar vein Lumbar veins Right gonadal vein Left gonadal vein Common iliac vein External iliac vein Internal iliac vein (a) Tributaries of the inferior vena cava; venous drainage of the paired abdominal organs.

Tributaries of the Inferior Vena Cava Right Left Diaphragm Hepatic veins Inferior vena cava Renal veins Abdominal aorta Common iliac veins (b) Dissection of the posterior abdominal wall illustrating abdominal vessels.

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 Inferior vena cava (not part of hepatic portal system) Hepatic veins Gastric veins Liver Spleen Inferior vena cava Hepatic portal vein Splenic vein Right gastroepiploic vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine Rectum (b) The veins of the hepatic portal system

Veins of the Pelvis & Lower Limbs Deep veins Share the name of the accompanying artery Superficial veins Great saphenous vein empties into the femoral vein

Veins of the Right Lower Limb & Pelvis Popliteal vein Common iliac vein Fibular vein Anterior tibial vein Dorsalis pedis vein Dorsal venous arch Dorsal metatarsal veins (a) Anterior view Internal iliac vein External iliac vein Inguinal ligament Great saphenous vein (superficial) Small saphenous vein Femoral vein

Questions…. What’s Next Questions…? What’s Next? Lab: Blood & Blood Vessels Mon Lecture: Finish material & Rev Mon Lab: Lab Exam 4! Wed Lecture: Lecture Exam 4!