5.1 Body Systems for Barbers: Nervous, Circulatory, Lymphatic, Endocrine and Integumentary
Key Takeaways
The nervous system has the central nervous system (brain and spinal cord), the peripheral nervous system and the autonomic nervous system; sensory nerves carry impulses to the brain and motor nerves carry them to muscles.
The common carotid artery divides into the internal carotid (brain, eyes, forehead) and the external carotid (face, scalp and neck); the internal and external jugular veins return blood from the head.
Blood is about 55% plasma; red blood cells carry oxygen, white blood cells fight infection and platelets help blood clot.
Endocrine glands, such as the pituitary, thyroid, adrenals, pancreas and gonads, are ductless and release hormones into the blood; androgens and thyroid hormone both affect hair growth.
The integumentary system is the skin together with its appendages: hair, nails and the sweat and oil glands.
Why Body Systems Matter at the Chair
The NIC Barber 1 outline asks candidates to understand the functions of the nervous, circulatory, endocrine and integumentary systems. These systems explain why massage relaxes a client, why a warm towel turns the skin pink, why shaving near the carotid pulse needs a light touch, and why hormones change beard and scalp hair. (Bones and muscles are covered in Section 4.1.)
| System | Main organs | Barbering connection |
|---|---|---|
| Nervous | Brain, spinal cord, nerves | Massage effects, motor points, sensation, reflexes |
| Circulatory | Heart, arteries, veins, capillaries, blood | Skin color, warmth, healing, bleeding, the pulse points to avoid |
| Lymphatic and immune | Lymph, lymph vessels, lymph nodes | Removing waste, fighting infection, swollen glands as a contraindication |
| Endocrine | Ductless glands and hormones | Hair growth, hair loss, beard development, oil production |
| Integumentary | Skin, hair, nails, sweat and oil glands | Everything a barber touches (Sections 4.2, 5.2 and 5.3) |
The Nervous System
- Central nervous system (CNS): the brain and spinal cord.
- Peripheral nervous system (PNS): the nerves that connect the CNS to the rest of the body, including 12 pairs of cranial nerves and 31 pairs of spinal nerves.
- Autonomic nervous system (ANS): controls involuntary functions such as heartbeat, sweat glands and the arrector pili muscles. It has two branches: the sympathetic ("fight or flight") and the parasympathetic ("rest and digest"). A calm scalp massage encourages a parasympathetic response.
A neuron (nerve cell) has dendrites that receive impulses and an axon that sends them on.
- Sensory (afferent) nerves carry impulses from the skin to the brain: touch, heat, cold, pressure and pain.
- Motor (efferent) nerves carry impulses from the brain to muscles.
- A reflex is an automatic response, such as a client flinching from a hot towel before they consciously feel the heat.
Nerves of the Head and Neck
The fifth (trigeminal), seventh (facial) and eleventh (accessory) cranial nerves are described in Section 4.1. The cervical nerves come from the spinal cord in the neck and supply the back of the scalp and the neck:
| Cervical nerve | Area supplied |
|---|---|
| Greater occipital | Skin of the scalp at the back and top of the head |
| Smaller (lesser) occipital | Scalp and muscles behind the ear |
| Greater auricular | Face, ears, neck and parotid gland |
| Cervical cutaneous | Front and sides of the neck, down to the breastbone |
A motor point is where a motor nerve enters a muscle. Massage and electrical stimulation applied there produce the strongest response.
The Circulatory (Cardiovascular) System
The heart pumps blood through a closed system of vessels.
- Arteries carry oxygen-rich blood away from the heart.
- Veins return oxygen-poor blood to the heart. Veins have valves that prevent backflow, which is why massage strokes are directed toward the heart.
- Capillaries are tiny vessels where oxygen, nutrients and waste are exchanged. Capillaries in the dermal papilla nourish the hair bulb.
Blood is roughly 55% plasma (water carrying nutrients, hormones and waste). The rest is formed elements:
- Red blood cells (erythrocytes) carry oxygen on hemoglobin.
- White blood cells (leukocytes) destroy pathogens. Pus is largely dead white cells.
- Platelets (thrombocytes) help blood clot, which is what stops a razor nick from bleeding.
Blood Supply of the Head, Face and Neck
The internal and external jugular veins, one pair on each side of the neck, return blood from the head to the heart. The carotid pulse can be felt beside the larynx. Pressing hard there, especially over the carotid sinus, can slow the heart and cause dizziness or fainting. Use only light pressure on the front and sides of the neck.
At the chair: Warm towels and massage dilate surface capillaries (the skin reddens and warms). A cold towel constricts them, which is one reason a cool towel finishes a shave.
The Lymphatic and Immune System
Lymph is a clear fluid that bathes the cells and carries waste back toward the bloodstream. Lymph nodes filter it and house white blood cells. Nodes sit at the angle of the jaw, behind the ears, at the back of the skull and along the neck. Swollen, tender nodes can signal infection, so be cautious about massaging over them. Gentle effleurage directed toward the nodes supports lymph flow.
The Endocrine System
Endocrine glands are ductless: they release hormones directly into the bloodstream. Exocrine glands, such as the sudoriferous (sweat) and sebaceous (oil) glands, deliver their secretions through ducts.
| Gland | Role | Hair and skin connection |
|---|---|---|
| Pituitary | The "master gland" that regulates other glands | Controls growth and puberty hormones |
| Thyroid (and parathyroids) | Metabolism (and calcium balance) | An underactive or overactive thyroid can cause diffuse hair thinning and dry or oily skin |
| Adrenals | Stress hormones (cortisol, adrenaline) and some androgens | Prolonged stress can contribute to shedding (telogen effluvium) |
| Pancreas | Insulin regulates blood sugar | Diabetes slows healing; take extra care with nicks and infections |
| Gonads (testes and ovaries) | Sex hormones (testosterone, estrogen) | Androgens drive beard growth, oil production, and male pattern hair loss in genetically sensitive follicles |
| Pineal | Melatonin and sleep cycles | — |
The Integumentary System
The integumentary system is the skin and its appendages: hair, nails, sudoriferous (sweat) glands and sebaceous (oil) glands. It protects the body, senses the environment, helps regulate temperature through sweat and blood flow, excretes some waste in sweat, and produces vitamin D with sunlight. Its structure and disorders are covered in Sections 5.2 and 5.3. Hair is covered in Sections 4.2 and 4.5.
Which branch of the external carotid artery supplies blood to the sides and top of the head, including the temples?
The facial artery
The internal carotid artery
The occipital artery
The superficial temporal artery
How do endocrine glands differ from sebaceous and sudoriferous glands?
Endocrine glands are ductless and release hormones into the bloodstream; sebaceous and sweat glands release secretions through ducts
Endocrine glands are found only in the scalp, while sebaceous glands are found only on the face
Endocrine glands produce sebum, and sebaceous glands produce hormones
There is no difference; all glands release secretions through ducts onto the skin
A client's skin turns pink while a warm steam towel is on the face and pales after a cold towel. What explains this?
Melanin production speeds up and then stops
Lymph nodes swell and then drain
Surface capillaries dilate with heat and constrict with cold
Motor nerves contract the arrector pili and then relax them
Sections you finish are checked off in the contents.