anatomy & physiology 2 Cardiovascular System

Common iliac artery Internal iliac artery

(bladder, pelvic walls, external genitalia, medial side of thigh, in females, uterus and vagina) • Lateral sacral artery • Internal pudendal artery • Obturator artery • Superior gluteal artery

Digital veins

(empty from thumb and fingers)

Pulmonary circuit

(to and from lungs)

Systemic circuit

(to and from rest of body)

Tunica intima

(tunica interna): innermost layer • Endothelial cells, connective tissue with elastic fibers In arteries, internal elastic membrane

Venous system( systemic vessels)

All drain into: • Superior vena cava (upper limbs, head, and neck) • Inferior vena cava (trunk and lower limbs)

Systemic Vessels

Arteries and veins are usually similar on both sides of body • One significant difference between arteries and veins is distribution in the neck and limbs • Arteries: deep in skin, protected by bones and soft tissues • Veins: generally two sets, one deep and one superficial; important in controlling body temperature • Venous blood flows superficially in hot weather to radiate heat • Venous blood flows deep in cold weather to conserve heat

Five general blood vessel classes

Arteries,arterioles, capillaries venules, and veins

Fetal Circulation and Defects

At birth, fetal circulation changes due to activated pulmonary circulation • Resulting pressure closes foramen ovale Fossa ovalis (shallow depression, adult remnant) • Rising oxygen levels cause ductus arteriosus to constrict and close Ligamentum arteriosum (fibrous adult remnant) 2Congenital cardiac defects • Ventricular septal defects Openings in interventricular septum • Patent foramen ovale Passageway remains open Left ventricle must work harder to provide adequate systemic flow • Patent ductus arteriosus Passageway remains open Blood is not adequately oxygenated and skin bluish Tetralogy of Fallot Complex group of defects • Pulmonary trunk is abnormally narrow (stenosis) • Interventricular septum is incomplete • Aorta originates where interventricular septum normally ends • Right ventricle enlarged • Atrioventricular septal defect: Both atria and ventricles are incompletely separated • Transposition of great vessels: Aorta is connected to right ventricle, pulmonary artery is connected to left ventricle

Arteries of the arm

Axillary artery (through axilla) • Brachial artery (upper limb)

Vessels of the Trunk: Veins

Azygos and hemiazygos veins (most of thorax) • Intercostal veins (chest muscles) • Esophageal veins (inferior esophagus) • Bronchial veins (passageways of lungs) • Mediastinal veins (mediastinal structures) Major tributaries of inferior vena cava • Lumbar veins (lumbar portion of abdomen) • Gonadal veins (gonads) • Hepatic veins (liver) • Renal veins (kidneys) • Adrenal veins (adrenal glands) • Phrenic veins (diaphragm)

Venous functional anatomy and pressure

Blood pressure in venules and medium veins is <10% of that in ascending aorta (largest artery) • These vessels contain valves (folds of tunica intima) that ensure one-way flow of blood toward heart Malfunctioning valves can lead to varicose veins (enlarged superifical thigh and leg veins) or distortion of adjacent tissues (hemorrhoids)

Functional Anatomy of Blood Vessels

Blood vessels conduct blood between heart and peripheral tissues

Branches of aortic arch

Brachiocephalic trunk • Right subclavian (right arm) • Right common carotid artery (right side head & neck) Left common carotid artery (left side head & neck) Left subclavian artery (left arm)

Veins of the arm

Cephalic vein (lateral side of arm) • Basilic vein (median side of arm) • Brachial vein (median area of arm) • Right subclavian vein Merging of axillary vein and cephalic vein

Head and Neck Vessels: Arteries

Common carotid artery (head and neck) Palpated alongside trachea (windpipe) Contains carotid sinus (with baroreceptors monitoring blood pressure) Branches of common carotid artery • External carotid artery (neck, esophagus, pharynx, larynx, lower jaw, cranium, and face on that side) • Internal carotid artery (brain and eyes) Vertebral artery (enters cranium and fuses with basilar artery along ventral medulla oblongata)

Fenestrated capillaries

Contain windows or pores penetrating endothelium • Permit rapid exchange of water and larger solutes • Examples: capillaries in brain and endocrine organs (pituitary, pineal and thyroid glands), absorptive areas of GI tract, kidney filtration sites

2 categories of capillaries

Continuous capillaries • Fenestrated capillaries

Arteries of the foot

Dorsalis pedis • Dorsal arch • Plantar arch • Medial plantar • Lateral plantar Lower

Vessels of the Brain: Veins

Dural sinuses drain superficial cerebral veins and small brain stem veins Unpaired median sinuses • Superior sagittal sinus • Inferior sagittal sinus • Straight sinus • Cavernous sinus • Occipital sinus Paired lateral sinuses • Transverse sinuses • Sigmoid sinuses • Petrosal sinuses Vertebral vein • Receives blood from transverse sinus, occipital sinus, superficial veins of skull, and cervical vertebrae

2 categories of arteries

Elastic arteries: and Muscular arteries:

Continuous capillaries

Endothelium is a complete lining • Located throughout body in all tissues except epithelium and cartilage • Permit diffusion of water, small solutes, and lipid-soluble materials • Prevent loss of blood cells and plasma proteins • Some selective vesicular transport

Lower Limb Vessels: Veins

External iliac veins (lower limbs, pelvis, and lower abdomen) • Internal iliac veins (pelvic organs) • External and internal iliac fuse to form common iliac veins

Head and Neck Vessels: Veins

External jugular vein (cranium, face, lower jaw, and neck on that side) • Internal jugular vein (various cranial venous sinuses) • Vertebral vein (cervical spinal cord and posterior skull)

Veins of the neck

External jugular vein (drains superficial head & neck) • Internal jugular vein (drains deep head & neck) • Vertebral vein (cervical spinal cord and posterior skull)

External iliac artery

Femoral artery • Deep femoral artery • Femoral circumflex arteries (ventral and lateral skin and deep muscles of thigh) • Popliteal artery (posterior knee) • Posterior and anterior tibial arteries (leg) • Fibular artery (lateral leg)

Vessels of the Viscera: Arteries

Hepatic artery proper (liver) • Cystic (gallbladder) • Gastroduodenal (stomach and duodenum) • Right gastric (stomach) • Right gastroepiploic (stomach and duodenum) • Superior pancreaticoduodenal (duodenum)

Superior mesenteric artery

Inferior pancreaticoduodenal (pancreas and duodenum) • Right colic (large intestine) • Ileocolic (large intestine) • Middle colic (large intestine) • Intestinal arteries (small intestine)

Right subclavian artery branches

Internal thoracic artery (pericardium, anterior chest wall) • Vertebral artery (brain, spinal cord)

Veins draining into superior vena cava (SVC)

Internal thoracic vein (intercostal veins) • Brachiocephalic vein (jugular, axillary, vertebral, and internal thoracic veins)

Inferior mesenteric artery

Left colic (colon) • Sigmoid (colon) • Rectal (colon)

Inferior mesenteric vein and tributaries

Left colic (descending colon) • Sigmoid (sigmoid colon) • Superior rectal (rectum)

Branches of the splenic artery

Left gastroepiploic (stomach) • Pancreatic (pancreas)

Capillary Bed

Network of capillaries with several connections between arterioles and venules • Can have collateral arteries (functionally redundant) fusing to one arteriole (forming an arterial anastomosis) leading to capillary bed • Can be bypassed by arteriovenous anastomosis that directly connects arteriole to venule

Arterial system ( systemic vessels)

Originates from aorta (largest elastic vessel exiting left ventricle)

Major patterns of blood vessel organization

Peripheral arteries and veins are generally identical between left and right sides except near heart • Vessels change names as they branch or move into new areas • Tissues and organs are usually served by many arteries and veins • Anastomoses reduce impact of potential blockages (occlusions)

Arterioles

Poorly defined tunica externa and tunica media only 1-2 smooth muscle cells thick

Two circuits of Cardiovascular System

Pulmonary circuit and Systemic circuit Each circuit begins and ends with the heart and occurs in sequence

Arteries of the forearm

Radial artery (follows radius) • Ulnar artery (follows ulna) • Palmar arches (hand) • Digital arteries (thumb and fingers)

Sinusoids

Resemble fenestrated capillaries that are flattened and irregularly shaped • Commonly have gaps between endothelial cells • Basal lamina is thin or absent • Permit more water and solute (plasma proteins) exchange • Occur in liver, bone marrow, spleen, and many endocrine organs

General circulation pathway through circuits

Right atrium (entry chamber) from systemic circuit to right ventricle, to pulmonary circuit • Pulmonary circuit • Pulmonary arteries to pulmonary capillaries to pulmonary veins • Left atrium from pulmonary circuit to left ventricle, to systemic circuit • Systemic circuit • Systemic arteries to systemic capillaries to systemic veins

Arteries of pulmonary circuit differ from those in systemic circuit Pulmonary arteries carry deoxygenated blood.

Right ventricle pulmonary trunk (large artery) pulmonary arteries pulmonary arterioles pulmonary capillaries (surrounded by alveoli, where gas exchange occurs) pulmonary venules pulmonary veins left atrium

Increasing venous blood flow

Skeletal muscle contractions squeezing veins with valves • Sympathetically controlled constriction of veins (venoconstriction) Venoconstriction can maintain arterial blood volume

Venules

Small veins lacking tunica media, collect blood from capillaries

Vessels of the Trunk: Arteries

Somatic branches of thoracic aorta • Intercostal arteries (chest muscles and vertebral column) • Superior phrenic artery (superior diaphragm) Visceral branches of thoracic aorta • Bronchial arteries (lung tissues not involved in gas exchange) • Esophageal arteries (esophagus) • Mediastinal arteries (tissues of mediastinum) • Pericardial arteries (pericardium) Major paired abdominal aorta branches • Inferior phrenic arteries (inferior diaphragm and esophagus) • Adrenal arteries (adrenal glands) • Renal arteries (kidneys) • Gonadal arteries (gonads) • Lumbar arteries (vertebrae, spinal cord, abdominal wall) Major unpaired branches of abdominal aorta • Celiac trunk (three branches) • Left gastric artery (stomach and inferior esophagus) • Splenic artery (spleen and stomach arteries) • Common hepatic artery (arteries to liver, stomach, gallbladder, and proximal small intestine) • Superior mesenteric artery (pancreas, duodenum, most of large intestine) • Inferior mesenteric artery (colon and rectum)

Veins of the forearm

Superficial palmar arch (hand) • Median antebrachial vein (anterior forearm) • Cephalic vein • Basilic vein • Median cubital vein (interconnects cephalic and basilic veins) Venous samples usually collected here

Hepatic portal vein tributaries

Superior mesenteric vein and tributaries • Pancreaticoduodenal • Middle colic (transverse colon) • Right colic (ascending colon) • Ileocolic (Ileum and ascending colon) • Intestinal (small intestine)

Capillaries

Thin, exchange vessels

Unique fetal circulation structures

Umbilical arteries (internal iliac arteries to placenta) • Umbilical vein (placenta to ductus venosus) • Ductus venosus (drains liver and umbilical vein into inferior vena cava) • Ductus arteriosus (pulmonary trunk to aorta) Sends blood from right ventricle to systemic circuit • Foramen ovale (right to left atrium) Has one-way valve to prevent backflow

Total blood volume distribution

Unevenly distributed between arteries, veins, and capillaries • Systemic venous system contains nearly 2/3 of total blood volume (~3.5 L) Of that , ~1 L is in venous networks of liver, bone marrow, and skin

Vessels of the Brain: Arteries

Vertebral arteries and internal carotid arteries supply brain Branches of internal carotid artery • Ophthalmic artery (eyes) • Anterior cerebral artery (frontal and parietal lobes of brain) • Middle cerebral artery (midbrain and lateral surfaces of cerebral hemispheres) Cerebral arterial circle (circle of Willis) • Formed by internal carotid arteries and basilar artery • Encircles infundibulum of pituitary gland Arrangement reduces likelihood of serious interruption of cerebral blood

Thoroughfare channels:

direct passages through capillary bed

Elastic arteries:

large vessels close to the heart that stretch and recoil when heart beats

veins

medium sized and large veins

Muscular arteries:

medium-sized arteries, distribute blood to skeletal muscles and internal organs

Thoroughfare channels begin with

metarteriole segment that can constrict or dilate to control flow • Has multiple capillaries connecting to venules • Have bands of smooth muscle (precapillary sphincters) to control flow into capillary bed Vasomotion: cycling contraction and relaxing changing capillary bed flow

Tunica media:

middle layer • Contains concentric sheets of smooth muscle Capable of vasoconstriction or vasodilation • Collagen fibers connect tunica media to other layers

Typical capillary consists

of tube of endothelial cells with delicate basal lamina • Neither tunica intima nor externa are present • Average diameter = 8 μm • About the same as an RBC

Tunica externa:

outermost layer • Connective tissue sheath with collagen and elastic fibers • Generally thicker in veins • Anchor vessel to surrounding tissues

Large veins:

superior and inferior venae cavae and tributaries having thin tunica media

Both arteries and veins have three layers

tunica intima, tunica media, and tunica externa

Medium-sized veins:

tunica media is thin but tunica externa is thick with longitudinal collagen and elastic fibers

Hepatic portal vein tributaries (continued) Splenic vein and tributaries

• Left gastroepiploic (stomach) • Right gastroepiploic (stomach) • Pancreatic