4.6 The Circulatory System & Facial Vasculature
Key Takeaways
- The adult body contains roughly 8 to 10 pints (about 5 liters) of blood, accounting for approximately 8% of total body weight.
- Blood is approximately 45% formed elements by volume (hematocrit) and 55% plasma, which is itself about 90% water.
- Red blood cells are biconcave discs carrying oxygen via hemoglobin; white blood cells constitute less than 1% of blood volume and provide immune defense.
- The common carotid arteries supply the head and face, while the internal and external jugular veins return blood from the head to the heart.
- Facial massage strokes are directed to support venous return and lymphatic drainage rather than to force blood into already congested capillary beds.
4.6 The Circulatory System & Facial Vasculature
The vitality, tone, and regenerative capacity of the skin depend directly on internal fluid dynamics and metabolic waste elimination. An in-depth understanding of the circulatory (cardiovascular), lymphatic (immune), excretory, endocrine, and respiratory systems enables licensed estheticians to perform treatments safely and effectively.
1. The Circulatory / Cardiovascular System
The circulatory system (cardiovascular system) is the closed vascular network responsible for transporting blood, dissolved oxygen, nutrients, hormones, and metabolic waste products throughout the human body.
VASCULAR NETWORK
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ARTERIES CAPILLARIES VEINS
• High pressure • Microscopic single-layer • Low pressure
• Carry oxygenated blood endothelial walls • Carry deoxygenated blood
away from heart • Site of nutrient & gas back to heart
• Thick, elastic walls interstitial exchange • Contain ONE-WAY VALVES
The Heart and Circulatory Pathways
The heart is a muscular, cone-shaped organ situated in the thoracic cavity, enclosed in a protective fibroserous sac called the pericardium. It operates as a dual muscular pump featuring four internal chambers:
- Right Atrium & Right Ventricle: Receive deoxygenated blood returning from systemic body tissues and pump it into the pulmonary circulation toward the lungs for carbon dioxide release and oxygenation.
- Left Atrium & Left Ventricle: Receive freshly oxygenated blood from the pulmonary veins and pump it into the systemic circulation via the aorta to nourish every living cell in the body.
The Three Types of Blood Vessels
- Arteries: Thick-walled, muscular, highly elastic vessels that transport oxygenated blood away from the heart under high hydrostatic pressure. (Exception: The pulmonary artery carries deoxygenated blood to the lungs). Arteries branch into smaller vessels called arterioles.
- Capillaries: Microscopic, delicate blood vessels with walls only one cell layer thick. They connect arterioles with venules and serve as the exclusive site of gas, nutrient, fluid, and metabolic waste exchange between circulating blood and surrounding interstitial tissues.
- Veins: Thin-walled, less elastic vessels that collect deoxygenated blood from venules and return it back to the heart under low pressure. Because venous blood travels against gravity from the extremities, veins are equipped with internal one-way pocket valves that prevent the backflow (retrograde flow) of blood.
Blood Composition and Characteristics
The adult human body contains approximately 8 to 10 pints (4.5 to 5.5 liters) of blood, accounting for approximately 8% of total body weight. Normal blood is slightly alkaline, with a pH ranging between 7.35 and 7.45, and maintains an internal temperature of ~98.6°F (37°C).
| Blood Component | Formed Element / Percentage | Primary Physiological Function | Esthetic & Skin Health Connection |
|---|---|---|---|
| Erythrocytes (Red Blood Cells / RBCs) | ~45% of blood volume (hematocrit); biconcave discs | Synthesized in red bone marrow; contain hemoglobin (iron-rich protein) that binds and delivers oxygen ($O_2$) to all body tissues | Delivers essential oxygen to basal keratinocytes and dermal fibroblasts; adequate microcirculation yields a rosy, healthy complexion |
| Leukocytes (White Blood Cells / WBCs) | <1% of blood volume | Primary immune defense cells; destroy pathogenic bacteria, viruses, and foreign debris via phagocytosis and antibody production | Neutralizes acne pathogens (Cutibacterium acnes) and accelerates post-inflammatory wound healing |
| Thrombocytes (Platelets) | Cellular fragments | Essential components of the blood clotting mechanism; aggregate at sites of vascular injury to form hemostatic plugs | Initiates wound healing cascades following microneedling, chemical peels, or minor abrasions |
| Plasma | ~55% of total blood volume; 90% water | Fluid extracellular carrier transporting dissolved proteins (albumin, fibrinogen, globulin), glucose, lipids, amino acids, hormones, and mineral salts | Delivers topical product nourishment absorbed through capillary beds; removes dissolved metabolic waste products |
2. Vascular Anatomy of the Head, Face, and Neck
Estheticians must possess precise anatomical knowledge of the major arteries and veins traversing the head, face, and neck to safely perform facial massage, contouring, and electrotherapy.
COMMON CAROTID ARTERY
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INTERNAL CAROTID ARTERY EXTERNAL CAROTID ARTERY
• Enters cranial vault • Supplies face, scalp, and neck
• Supplies brain, eye orbit, • Primary facial branches:
and forehead (supraorbital) - Facial Artery (Ext. Maxillary)
- Superficial Temporal Artery
- Occipital & Post. Auricular
Arterial Supply to the Head and Face
The primary arterial blood supply to the head and neck is delivered by the common carotid arteries, which ascend on each side of the anterolateral neck. At the level of the upper thyroid cartilage (Adam's apple), each common carotid divides into two major trunks:
- Internal Carotid Artery: Ascends deeply into the skull without branching in the neck to supply the brain, eye orbits, and deep cranial structures. It emerges onto the face via the supraorbital artery (supplying the forehead and upper eyelid) and the supratrochlear artery.
- External Carotid Artery: Supplies the superficial structures of the face, scalp, and neck. Its critical branches in esthetics include:
- Facial Artery (External Maxillary Artery): Crosses over the lower border of the mandible near the anterior angle; supplies the lower face, mouth, and nose. Key sub-branches include:
- Inferior Labial Artery: Supplies blood to the lower lip.
- Superior Labial Artery: Supplies blood to the upper lip and septum of the nose.
- Angular Artery: Terminal branch ascending alongside the nose to the inner canthus of the eye.
- Submental Artery: Supplies blood to the chin and lower lip.
- Superficial Temporal Artery: Ascends anterior to the ear, supplying the temporal region and branching into:
- Frontal Artery: Supplies the forehead.
- Parietal Artery: Supplies the crown and lateral scalp.
- Transverse Facial Artery: Supplies the masseter muscle and cheek.
- Occipital Artery: Supplies blood to the posterior scalp and occipital muscles.
- Posterior Auricular Artery: Supplies the scalp above and behind the ear.
- Facial Artery (External Maxillary Artery): Crosses over the lower border of the mandible near the anterior angle; supplies the lower face, mouth, and nose. Key sub-branches include:
Venous Drainage of the Head and Neck
Deoxygenated blood returns from the head, face, and neck through two primary sets of veins:
- Internal Jugular Vein: Located deeply along the carotid artery under the sternocleidomastoid; drains blood from the brain, cranial vault, and deep facial structures.
- External Jugular Vein: Located more superficially along the lateral aspect of the neck; drains blood from the superficial face, scalp, and exterior ear into the subclavian vein.
Which blood vessels possess thin walls, operate under low hydrostatic pressure, and are equipped with internal one-way valves to prevent the backward flow of deoxygenated blood?
Which artery is a major branch of the external carotid artery that crosses over the lower border of the mandible to supply blood to the lower face, mouth, and nose?