3.4 The Cardiovascular System & Circulation of the Face and Neck

3.4 The Cardiovascular System & Circulation of the Face and Neck

[!NOTE] Systemic Delivery and Hormonal Control: Cutaneous health is inextricably linked to systemic vascular perfusion, lymphatic fluid clearance, and endocrine equilibrium. Topical skincare cannot overcome chronic hypoxia, stagnant interstitial edema, or uncontrolled androgenic stimulation. Licensed estheticians must understand how blood circulation nourishes the dermis, how the lymphatic system purges waste, and how endocrine glands govern skin pathology.

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Cardiovascular Architecture and Hemodynamics

The circulatory (cardiovascular) system is an integrated closed vascular network comprising the heart, blood vessels, and blood. It continuously delivers oxygen, glucose, amino acids, and hormones to all living tissues while removing metabolic byproducts such as carbon dioxide and lactic acid.

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|                     Cardiovascular Dual Circulation Pattern                       |
+-----------------------------------------------------------------------------------+
| PULMONARY CIRCULATION:                                                            |
| Right Atrium ──> Tricuspid Valve ──> Right Ventricle ──> Pulmonary Arteries ──>   |
| Lungs (O2 Uptake / CO2 Release) ──> Pulmonary Veins ──> Left Atrium               |
|-----------------------------------------------------------------------------------|
| SYSTEMIC CIRCULATION:                                                             |
| Left Atrium ──> Bicuspid (Mitral) Valve ──> Left Ventricle ──> Aorta ──>          |
| Systemic Arteries ──> Arterioles ──> Capillaries (Tissue Nutrient Exchange) ──>   |
| Venules ──> Systemic Veins ──> Superior/Inferior Vena Cava ──> Right Atrium       |
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The Heart: Chambers and Valves

The heart is a hollow, muscular, conical organ situated in the thoracic cavity between the lungs, enclosed by a protective fibroserous sac called the pericardium. It weighs approximately 9 to 11 ounces and functions as a synchronized double pump featuring four internal chambers and four one-way valves:

• Right Atrium (Upper Right Chamber): Receives oxygen-depleted, venous blood returning from systemic body tissues via the superior vena cava (from head and arms) and inferior vena cava (from lower body).
• Right Ventricle (Lower Right Chamber): Receives blood from the right atrium through the tricuspid valve and pumps it into the pulmonary trunk through the pulmonary semilunar valve toward the lungs.
• Left Atrium (Upper Left Chamber): Receives newly oxygenated blood returning from the pulmonary capillaries via four pulmonary veins.
• Left Ventricle (Lower Left Chamber): The thickest, most muscular chamber of the heart. It receives oxygen-rich blood from the left atrium through the bicuspid (mitral) valve and forcibly contracts to eject blood through the aortic semilunar valve into the aorta for systemic distribution throughout the entire body.

Blood Vessel Types and Vascular Dynamics

Blood travels through an interconnected tree of specialized vessels:

1. Arteries: Thick-walled, elastic, muscular tubes that transport oxygen-rich blood away from the heart under high hydrostatic pressure. Arteries expand during cardiac systole and recoil during diastole to maintain continuous forward blood flow.
2. Arterioles: Small-diameter terminal branches of arteries that deliver blood into capillary beds. Arterioles are wrapped in smooth muscle and act as the primary regulators of systemic blood pressure and local cutaneous blood flow (vasomotor control).
3. Capillaries: Microscopic, single-cell-thick endothelial tubes connecting arterioles to venules. Capillaries are the true functional exchange vessels of the cardiovascular system. Their thin, semipermeable walls permit oxygen, glucose, and amino acids to diffuse into the interstitial space to nourish dermal fibroblasts and basal keratinocytes, while absorbing carbon dioxide and cellular wastes into the bloodstream.
4. Venules: Minute vessels that collect deoxygenated blood from capillary networks and coalesce into larger veins.
5. Veins: Thin-walled, distensible vessels that return deoxygenated blood from the tissues back toward the heart under low pressure. Because venous pressure is low, veins are equipped with internal cup-like one-way valves that prevent the backflow and gravitational pooling of blood, particularly in the extremities and neck.

Composition of Blood

Whole blood is a sticky, slightly alkaline fluid (pH 7.35 to 7.45) that constitutes approximately 8% of total adult body weight (about 8 to 10 pints / 4 to 5 liters). It consists of two major fractions:

• Plasma (55% of Blood Volume): A straw-colored, fluid extracellular matrix composed of approximately 90% water and 10% dissolved solutes. Plasma solutes include vital plasma proteins (albumin maintaining oncotic osmotic pressure, globulins serving as antibodies, and fibrinogen required for blood clotting), electrolytes (Na+, K+, Ca2+), glucose, lipids, metabolic enzymes, hormones, and waste products (urea, creatinine).
• Formed Cellular Elements (45% of Blood Volume):
  • Erythrocytes (Red Blood Cells / RBCs): Biconcave, flexible discs lacking nuclei that are produced in red bone marrow. They are densely packed with hemoglobin, an iron-containing complex protein that binds oxygen in the lungs and releases it to metabolizing skin cells, while binding carbon dioxide for pulmonary excretion.
  • Leukocytes (White Blood Cells / WBCs): Nucleated defense cells that protect the body against infectious microorganisms, foreign antigens, and toxins. Leukocytes perform phagocytosis (engulfing bacteria and debris) and produce neutralizing antibodies.
  • Thrombocytes (Platelets): Small, disc-shaped, non-nucleated cellular fragments derived from bone marrow megakaryocytes. Platelets adhere to damaged endothelial surfaces, initiating the blood coagulation cascade to form fibrin clots and halt hemorrhage.

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Arterial and Venous Pathways of the Head, Face, and Neck

The vascularization of the head, face, and neck is derived from the common carotid arteries, which ascend on either side of the trachea in the anterior neck.

                             COMMON CAROTID ARTERY
                                       │
         ┌─────────────────────────────┴─────────────────────────────┐
         ▼                                                           ▼
  INTERNAL CAROTID                                            EXTERNAL CAROTID
  (Brain, Eyes, Forehead)                                   (Face, Scalp, Neck)
         │                                                           │
         └──> Ophthalmic Artery                                      ├──> Facial (Ext. Maxillary) Artery
              ├──> Supraorbital                                      ├──> Superficial Temporal Artery
              └──> Supratrochlear                                    ├──> Occipital Artery
                                                                     └──> Posterior Auricular Artery

Arteries of the Head, Face, and Neck

At the superior level of the thyroid cartilage (Adam's apple), each common carotid divides into two primary trunks:

1. Internal Carotid Artery: Ascends deeply into the cranium to supply the brain, meninges, and internal cranium. Its crucial external branch is the ophthalmic artery, which emerges through the orbital rim to supply the eye, tear glands, eyelids, and forehead via the supraorbital and supratrochlear arteries.
2. External Carotid Artery: Ascends anteriorly to supply the superficial structures of the face, scalp, mouth, tongue, and neck. It gives off four critical branches of direct importance to esthetic treatments:
   • Facial Artery (External Maxillary Artery): Curves over the lower border of the mandible anterior to the masseter muscle to supply the lower face, mouth, and nose. Key sub-branches include:
     • Submental Artery: Supplies the chin and lower lip.
     • Inferior Labial Artery: Supplies the lower lip.
     • Superior Labial Artery: Supplies the upper lip and nasal septum.
     • Angular Artery: Terminal branch ascending along the side of the nose to supply the lacrimal sac and medial eye.
   • Superficial Temporal Artery: The continuation of the external carotid artery as it ascends directly in front of the ear. It branches into:
     • Transverse Facial Artery: Supplies the masseter muscle and lateral cheek.
     • Frontal (Anterior) Branch: Supplies the forehead and frontalis muscle.
     • Parietal (Posterior) Branch: Supplies the crown and parietal scalp.
   • Occipital Artery: Passes posteriorly beneath the sternocleidomastoid muscle to supply the occipital scalp and muscles of the posterior neck.
   • Posterior Auricular Artery: Ascends behind the ear to supply the external auricle and the scalp above and behind the ear.

Veins of the Head, Face, and Neck

Deoxygenated blood returns from the cranial and facial tissues through two major jugular veins situated on each side of the neck:

• Internal Jugular Vein: A large, deep venous trunk running adjacent to the internal carotid artery. It drains blood from the brain, meninges, orbits, and deep facial structures via the facial and lingual veins.
• External Jugular Vein: A more superficial vein that descends across the outer surface of the sternocleidomastoid muscle beneath the platysma. It collects blood from the superficial scalp and outer facial regions, emptying into the subclavian vein at the root of the neck.

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