CIRCULATION: Arteries, Veins and Their Pathways

Circulatory System: Comprehensive Notes

The following notes are derived from the provided transcript. Some items reflect slide wording that may include simplifications or context-specific phrasing (e.g., embalming-focused content). Cross-check with standard anatomy references when in doubt. Explanations emphasize both the material in the transcript and generally accepted physiology where applicable.

Veins vs. Arteries

From transcript: Veins vs. Arteries – general comparison
- Carry blood toward the heart
- Do not stretch
- May be superficial
- Blue color
- Collapse when incised
- May be accompanied by an artery
- Usually larger than artery
- More numerous than arteries
- Carry blood away from heart
- Elastic
- Deep/well protected
- Cream color
- Feels like a large rubber band
- Stand open when incised
- Always accompanied by vein
Note: Some points above reflect slide phrasing that may blend or invert typical anatomical facts (e.g., veins usually accompany arteries but arteries are typically accompanied by veins; veins are not universally “larger than arteries”). Use these as study prompts and verify with standard physiology for exam readiness.

Vessel Wall Structure and Cross-Sectional Anatomy

Endothelium: innermost lining of vessels
Smooth muscle: chiefly in tunica media; regulates constriction/dilation
External elastic lamina: layer separating media from adventitia in arteries
Adventitia (externa): outermost connective tissue layer
Basal lamina: basement membrane underlying endothelium
Lumen: central hollow space through which blood flows
Erythrocyte (red blood cell): primary cell carried in blood
Pericyte: supporting cell associated with capillaries
Internal elastic lamina: elastic boundary within tunica interna
Basement membrane: supporting matrix for endothelial cells
Capillaries: smallest vessels, site of exchange
Artery: vessel carrying blood away from heart
Arterioles: small arteries leading to capillaries
Vein: vessel carrying blood toward the heart
Thoroughfare channel: fastest-capacitance route within microcirculation (context-specific term)
Adventitia (repeated): connective tissue layer surrounding larger vessels

General Vessel Structure (Arteries, Veins, Capillaries)

Capillaries: capillary network with lumen very small; site of gas and nutrient exchange
Vessel walls vary by type (arteries vs veins): thicker, more elastic walls in arteries; thinner walls in veins with larger lumens
Vasa vasorum: small vessels supplying the walls of larger arteries and veins

Arteries: Tunic Layers and Features

Tunica externa (Adventitia): outermost layer of arteries; composed of loose connective tissue; function is anchoring, protection, and preventing overstretching
Tunica media: middle layer; composed of smooth muscle; controls dilation and constriction of vessels
Tunica interna (Intima): innermost layer; lined by endothelium
Internal elastic membrane: elastic boundary between intima and media
External elastic membrane: elastic boundary between media and externa
Tunica externa: collagen fibers providing structural support
Vasa vasorum: small vessels that perfuse the vessel walls
Lumen: central open channel for blood flow
Capillary network: connected to arteries/arterioles and veins/venules for exchange

Embalming Focus on the Blood Vascular System

The transcript highlights that embalming focuses on the blood vascular system, underscoring its central role in circulatory pathways.

The Blood Vascular System: Overview

Closed system
Works in a circle (cyclical pathway)
Heart acts as the pump to drive circulation
Arteries and arterioles deliver blood from the heart to tissues
Capillaries disperse blood to exchange sites and usage areas
Venules and veins return used blood to the heart for recirculation

Functions of the Blood Vascular System

Transportation: delivers oxygenated blood to tissues
Gas exchange: enables delivery of gases (O2 to tissues; CO2 from tissues)
Veins return spent blood to the heart for reoxygenation/recycling

The Heart: Pump and Pressure/Flow

The heart must generate pressure and sustain a rate of flow to function as a pump
The beating heart creates the driving pressure for circulation

Characteristics and Anatomy of the Heart

The Heart:
- Hollow muscular organ
- Located in the mediastinal cavity of the thorax
- Mediastinal contents include thymus, esophagus, trachea
- Positioned between the lungs
- Above the diaphragmatic central area; slightly left of the midline
Surrounding the Heart: Pericardium
- Pericardium is a sac around the heart
- Two layers: serous pericardium (closest to the heart) and fibrous pericardium (outer layer, attaches heart to mediastinal cavity)
- Pericardial fluid sits between layers to reduce friction
Pericardial Layers (visual cues from slides)
- Serous pericardium lies closest to the heart
- Fibrous pericardium is the outer coating

Dimensions and Weight of the Heart

Approximate size: closed fist
Length: $12 ext{ cm} <br /> ightarrow ext{approximately } 12 ext{ cm}$
Width: $8{-}9 ext{ cm} <br /> ightarrow ext{approximately } 8 ext{–}9 ext{ cm}$
Thickness: $6 ext{ cm} <br /> ightarrow ext{approximately } 6 ext{ cm}$
Average weight: $250{-}300 ext{ g} <br /> ightarrow ext{roughly } 250 ext{-}300 ext{ g}$

Layers of the Heart

Epicardium: outer layer (visceral pericardium)
Myocardium: thick cardiac muscle tissue; responsible for contraction
Endocardium: inner lining of the heart chambers
Pericardial cavity: space between layers of the pericardium
Pericardium (fibrous layer): outer protective sac
Parietal pericardium: part of serous pericardium lining the pericardial sac
Visceral pericardium (epicardium): closely adheres to the heart surface

Chambers of the Heart

Four chambers total:
- Two atria (receiving chambers): located in the upper part of the heart
- Two ventricles (pumping chambers): located in the lower part of the heart

Blood Movement Through the Chambers (General Flow)

Right atrium receives blood from the systemic circulation (deoxygenated blood)
Right ventricle ejects blood into the pulmonary circulation via the pulmonary artery
Left atrium receives blood from the pulmonary circulation (oxygenated blood)
Left ventricle ejects blood to the systemic circulation via the aorta

Major Vessels Associated with Heart Circulation

Right side:
- Superior vena cava
- Inferior vena cava
- Right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary artery (to lungs)
- Pulmonary valve (valve at the exit from the right ventricle into the pulmonary trunk)
Left side:
- Pulmonary veins (from lungs to left atrium)
- Left atrium
- Mitral (bicuspid) valve
- Left ventricle
- Aortic valve
- Aorta (ascending, arch, descending sections)
Pericardium surrounds the whole heart

Valves of the Heart

Function: close chambers to prevent regurgitation and ensure unidirectional flow
Valves are made up of cusps (flaps) that close the passage when the chamber relaxes/opens elsewhere
Bicuspid (Mitral) valve: two cusps
Tricuspid valve: three cusps
Valve integrity is essential to prevent conditions like heart murmurs, prolapse, and other cardiac diseases

Right-Sided and Left-Sided Circulation (Pulmonary vs Systemic)

Right ventricle → Pulmonary artery → Lungs → Pulmonary veins → Left atrium
Pulmonary circulation carries deoxygenated blood to the lungs for oxygenation
Left ventricle → Aorta → Systemic circulation → Tissues throughout the body
This creates two concurrent circuits: a pulmonary circuit (right heart to lungs) and a systemic circuit (left heart to body)

Right Ventricle and Pulmonary Circulation (Key Points)

Right ventricle pumps blood into the pulmonary artery
Pulmonary artery carries deoxygenated blood to the lungs
Lungs oxygenate blood
Blood returns to the heart via pulmonary veins into the left atrium

Left Side Circulation (Key Points)

Left atrium receives oxygenated blood from the lungs via pulmonary veins
Blood moves through the mitral valve to the left ventricle
Left ventricle pumps blood into the aorta via the aortic valve
Aorta distributes oxygenated blood to the systemic circulation

Right Side and Left Side Vessel Details (Illustrated Pathways)

Right atrium → Tricuspid valve → Right ventricle → Pulmonary valve → Pulmonary artery → Lungs → Pulmonary veins → Left atrium
Left atrium → Mitral valve → Left ventricle → Aortic valve → Ascending aorta → Arch of the Aorta → Descending Aorta → Systemic arteries to the body

The Aorta and Its Branches

Arch of the Aorta gives rise to major branches that supply the head, neck, and upper limbs
1st branch off the Arch of Aorta: Brachiocephalic Trunk (also called Innominate Artery)
- Splits into Right Subclavian artery and Right Common Carotid artery
Left side branches from the Arch of the Aorta include Left Common Carotid artery and Left Subclavian artery
Descending Aorta continues from the Arch into the Thoracic Aorta and then the Abdominal Aorta
The Abdominal Aorta splits into Common Iliac Arteries at the level of the diaphragm

Arch of Aorta Branches and Pathways (Overview)

Arch of the Aorta → Brachiocephalic trunk → Right Subclavian artery and Right Common Carotid artery
Arch of the Aorta → Left Common Carotid artery
Arch of the Aorta → Left Subclavian artery
Ascending aorta continues to the arch; Aortic valve regulates flow from left ventricle to the aorta

Common Carotid Arteries and Branches

Right Common Carotid Artery: typically arises from the Brachiocephalic trunk; divides into:
- External Carotid Artery
- Internal Carotid Artery
Left Common Carotid Artery: direct branch off Arch of the Aorta; divides into
- External Carotid Artery
- Internal Carotid Artery
External Carotid Artery: supplies facial muscles, scalp, and superficial structures of the head
Internal Carotid Artery: supplies the eye and brain regions
Carotid bifurcation occurs where the common carotid splits into external and internal branches
Notable additional arteries shown: Vertebral artery, Thyrocervical trunk, Subclavian artery, etc.

Subclavian Arteries and Upper Limb Pathways

Right Subclavian Artery: branch of the Brachiocephalic trunk
Left Subclavian Artery: third branch off Arch of the Aorta
Subclavian arteries become Axillary arteries as they pass the lateral border of the first rib
Axillary Artery → Brachial Artery
Brachial Artery branches into:
- Ulnar Artery
- Radial Artery

Arteries of the Hand and Forearm

Forearm/Hand arterial network includes:
- Palmar arches (deep and superficial)
- Palmar arteries (common and proper)
- Metacarpal arteries
- Proper digital arteries
Hand-specific arteries include the Princeps Pollicis artery (artery supplying the thumb)

Thoracic and Abdominal Aorta: Major Branches

Arch of the Aorta branches into head/upper limb vessels
Descending Aorta flows through the thorax (Thoracic Aorta) and abdomen (Abdominal Aorta)
Abdominal Aorta gives rise to: Renal arteries, Superior Mesenteric, Gonadal, Inferior Mesenteric, Celiac trunk, External Iliac, Internal Iliac, and more
Common Iliac Arteries: split into Internal and External Iliac arteries; external iliac becomes femoral artery in the thigh

Arteries of the Pelvis and Legs: Core Pathways

Pelvic and leg arteries include:
- Common Iliac Arteries (split into Internal Iliac and External Iliac)
- External Iliac Artery becomes Femoral Artery after passing under the inguinal ligament
- Femoral Artery continues as Deep Femoral (profunda femoris) and then Popliteal Artery behind the knee
- Popliteal Artery splits into Anterior Tibial Artery and Posterior Tibial Arteries; Posterior Tibial gives rise to Fibular (Peroneal) Artery
- Dorsalis Pedis Artery on the foot; continues into Metatarsal Arteries and Plantar Arches

Arteries of the Legs: Key Branches

Femoral Artery (major leg artery)
Popliteal Artery (behind knee)
Anterior Tibial Artery
Tibial Arteries (posterior and anterior)
Fibular (Peroneal) Artery
Dorsalis Pedis Artery (on the dorsum of the foot)
Plantar Arch

Arteries of the Feet

Dorsalis Pedis Artery
Lateral Tarsal Artery
Arcuate Artery
Metatarsal Arteries
Proper Digital Arteries

Illustrative Notes on Pathways and Terminology

Some section headers mirror slide numbering (e.g., Arch of Aorta, Common Carotid, Subclavian), useful for exam-style recall of vessel order and branching relationships.
The transcript provides labeled flows and branch points that align with standard anatomical pathways, though some slide items may reflect simplified or context-specific phrasing (e.g., embalming-focused perspectives or diagrammatic labels).

Quick Reference: Summary of Key Pathways (Condensed)

Right side core: Arch gives Brachiocephalic trunk → Right Subclavian + Right Common Carotid
Left side core: Arch gives Left Common Carotid and Left Subclavian
Aorta progression: Ascending Aorta → Arch of the Aorta → Descending Aorta (Thoracic) → Abdominal Aorta → Common Iliac Arteries
Upper limb flow: Subclavian → Axillary → Brachial → Split into Ulnar and Radial
Hand/forearm: Ulnar and Radial feed Palmar arches (Deep and Superficial) and digital arteries
Head/neck: Common Carotids divide into External (face/scalp) and Internal (brain/eye) arteries
Leg/pelvis: Common Iliac → Internal/External Iliac → External becomes Femoral → Popliteal → Anterior Tibial, Tibial (Posterior), Fibular; dorsum of foot via Dorsalis Pedis and Plantar arches

Notation of LaTeX-ready references (where applicable)

Heart dimensions: $12 ext{ cm}$ (length); $8{-}9 ext{ cm}$ (width); $6 ext{ cm}$ (thickness)
Weight: $250{-}300 ext{ g}$
The two main circulatory pathways: Pulmonary circulation and Systemic circulation