1.1 Describe the anatomy and physiology of healthy skin

This guide will help you answer 1.1 Describe the anatomy and physiology of healthy skin.

Skin is the largest organ of the human body. It covers the entire body surface and plays a key role in protection, sensation, and temperature regulation. Healthy skin supports well-being and helps defend against infection.

Skin has a layered structure and many cells performing specific roles. Understanding its anatomy and physiology helps care workers support people’s health.

Layers of the Skin

Skin has three main layers. Each layer has a different structure and role.

Epidermis

The epidermis is the outer layer. It is visible and provides a barrier against the environment.

Main features of the epidermis:

• Made up of flat, closely packed cells
• Contains no blood vessels
• Constantly renews itself

Key cell types in the epidermis:

• Keratinocytes – produce keratin, which strengthens the skin and forms a waterproof barrier
• Melanocytes – produce melanin, a pigment that gives skin its colour and protects against sunlight
• Langerhans cells – help with immune defence
• Merkel cells – connect to nerves, providing a sense of touch

The top part of the epidermis is the stratum corneum. Dead keratin-filled cells make up this layer. These cells are shed regularly and replaced from below.

The bottom layer of the epidermis is the stratum basale (basal layer). This is where new cells are made before moving upwards.

Dermis

The dermis sits below the epidermis. It is much thicker and made of strong, flexible tissue.

Features of the dermis:

• Contains blood vessels
• Houses nerve endings
• Contains sweat and oil (sebaceous) glands
• Contains hair follicles
• Has connective tissue with proteins called collagen and elastin

Collagen gives skin strength, helping resist tearing. Elastin allows it to stretch and bounce back. Both are shaped by genetics and lifestyle.

The dermis is involved in:

• Supplying nutrients to the skin
• Supporting hair growth
• Producing sweat for cooling
• Providing touch, pain, and temperature sensations

Hypodermis (Subcutaneous Tissue)

The hypodermis lies under the dermis. This layer is made up of fat (adipose) tissue and connective tissue.

Roles of the hypodermis:

• Cushions the body from knocks
• Stores energy as fat
• Insulates against heat loss
• Helps anchor the skin to muscles and bones

In different body areas and between people, this layer can vary in thickness.

Functions of Healthy Skin

Healthy skin does much more than simply cover our bodies. Its functions keep the body safe, healthy, and balanced.

Protection

Skin is the primary barrier against bacteria and viruses. It helps prevent harmful substances from entering the body.

The toughness of keratin and tight packing of skin cells creates a sealed layer. Melanin pigment in the epidermis protects deeper tissues from ultraviolet (UV) rays, lowering risk of sunburn and skin cancer.

Sweat and sebum (skin oil) provide a slightly acidic film on the surface. This film discourages the growth of harmful microbes.

Sensation

Skin contains millions of nerve endings. These sense:

• Touch
• Pressure
• Pain
• Temperature
• Vibration

Special sensory receptors send signals through nerves to the brain. These allow quick reactions to hot, cold, or painful things.

Temperature Regulation

The skin helps keep the body temperature within a safe range.

Key ways the skin controls temperature:

• Sweat glands produce sweat, which cools the body as it evaporates
• Blood vessels in the dermis widen (dilate) or narrow (constrict) to increase or reduce heat loss

In the cold, blood vessels tighten and less warm blood flows near the surface. This keeps warmth in. In the heat, blood vessels widen and warm blood moves near the surface, allowing heat out.

Excretion

Sweat contains small amounts of waste, like urea and salt. When we sweat, these are removed from the body.

Synthesis of Vitamin D

When skin is exposed to sunlight, a chemical reaction starts that leads to the production of vitamin D. This vitamin is needed for healthy bones and teeth.

Absorption

Most substances do not pass through the skin. However, some small or fat-soluble chemicals can be absorbed, including some medicines (for example, nicotine patches).

Anatomy of Healthy Skin Structures

Different parts of the skin contain specialised structures.

Hair Follicles

Each hair grows from a tiny tube, or follicle, in the dermis. The base of the follicle contains living cells that divide to produce the hair shaft.

Attached to each follicle:

• Sebaceous gland – produces sebum (oil) to lubricate hair and skin
• Small muscle (arrector pili) – can make hair stand up when cold or afraid

Hair protects the scalp from sunlight and injury. Eyelashes defend the eyes and nostril hair helps filter dust.

Nails

Nails grow at the tips of fingers and toes. The nail root is under the cuticle, in the skin.

Main features:

• Made of hard keratin
• Protects the tips of fingers and toes
• Helps with gripping

Nail growth is affected by health, circulation, and nutrition.

Sweat Glands

There are two main types of sweat gland in the dermis:

• Eccrine glands: found all over the body, especially on palms, soles, and forehead. They open directly onto the skin and help control body temperature.
• Apocrine glands: found under the arms and in the groin. They open into hair follicles and become active during puberty.

Both types help get rid of waste and reduce temperature.

Sebaceous (Oil) Glands

These glands attach to hair follicles. They produce sebum, which:

• Lubricates skin and hair
• Stops skin drying out
• Helps prevent bacterial growth

Production of sebum increases during adolescence and can cause oily skin or spots.

Blood Vessels

The dermis contains a network of tiny blood vessels. These supply the outer layers with oxygen and nutrients, and remove waste products.

Quick changes in skin colour (flushing or blanching) reflect changes in blood flow.

Nerve Endings

Touch, temperature, and pain receptors are spread across the skin. Some areas, like lips and fingertips, are packed with nerves, making them extra sensitive.

Different nerve endings respond to different types of sensation. This enables detection of light touch, deep pressure, hot, and cold.

Physiology: How Healthy Skin Works

Healthy skin is always active. Each part of its structure contributes to the skin’s functions.

Cell Turnover

In the epidermis, new skin cells form at the base. As they move upwards:

• Cells produce more keratin
• Cells flatten and die to form the outer barrier
• Dead cells are shed from the surface

This process takes about a month. It allows the skin to recover quickly from injury.

Repair and Healing

If the skin is cut or damaged, it repairs itself.

• Platelets in blood form a clot to stop bleeding
• White blood cells fight any germs
• New cells grow and close the wound
• Scar tissue may form if the damage is deep

Young, healthy skin heals faster than older or damaged skin.

Colour and Pigmentation

Melanin gives skin its colour. Sunlight increases melanin production, leading to tanning.

People with darker skin have more melanin. Healthy skin shows an even tone. Patches or changes in colour can suggest problems.

Protection from Ultraviolet (UV) Rays

Too much sun exposure damages DNA in skin cells. Melanin helps protect against this by absorbing UV rays.

The skin produces more melanin as a natural defence. However, too much UV can still cause burns or cancer.

Moisture Balance

Sebum and sweat keep the skin flexible and stop it drying out. Dead cells and natural oils make a barrier that reduces water loss.

Too little moisture can cause cracks, itchiness, and infection risk. Too much oil can cause spots or acne.

Microbiome

A layer of harmless bacteria (known as ‘skin flora’) lives on healthy skin. These bacteria help stop dangerous microbes causing infection.

Washing, antibiotics, or illness can disturb the balance. Healthy skin supports a normal, balanced microbiome.

Factors Influencing Skin Health

Keeping skin healthy helps it function well. Different factors affect skin health.

Age

• Babies have thinner, more sensitive skin, making them prone to irritation and infection
• Older adults have drier, less elastic skin, with slower healing

Nutrition

A balanced diet helps skin renew and repair.

Important nutrients:

• Protein: needed for new cells
• Vitamins, especially A, C, E and D: support structure, repair, and protection from UV
• Minerals, such as zinc and selenium: assist healing and antioxidant defence
• Water: keeps skin flexible and prevents drying

Hydration

Drinking water prevents dryness and flakiness. Both dehydration and overhydration can change the skin’s appearance.

Sunlight Exposure

Small amounts of sunlight are good for vitamin D. Too much causes damage, ageing, and skin cancer risk.

Hygiene

Regular gentle washing gets rid of dirt, sweat, oil, and dead cells. Over-washing or harsh products can harm the skin’s barrier.

Injury and Infection

Cuts, burns, and infections affect skin structure and function. Healing depends on good blood supply, health, and care.

Medical Conditions

Problems like eczema, psoriasis, and diabetes can weaken the skin, reduce healing, or make it dry and fragile.

Skin Variations and Health

No two people have identical skin. Common differences include:

• Colour, based on melanin levels
• Oiliness and dryness
• Thickness and sensitivity
• Tendency to sunburn or tan

Healthy skin is generally:

• Intact, with no open wounds
• Even-coloured
• Free of infection or excessive scaling
• Comfortable, with no ongoing pain or itching

Common Problems Affecting Healthy Skin

Factors affecting skin health may include:

• Cuts, grazes, and wounds
• Rashes (like eczema or dermatitis)
• Acne
• Fungal infections (athlete’s foot, ringworm)
• Psoriasis
• Sunburn
• Ulcers, more common in people with reduced mobility or circulation problems

Supporting skin health in care settings means routine inspection, cleaning, and prompt response to changes.

Final Thoughts

Skin is a complex but familiar organ. Its structure includes the epidermis, dermis, and subcutaneous tissue, each supporting specific roles. Healthy skin protects the body, senses the environment, manages temperature, and enables healing.

Understanding the anatomy and physiology of healthy skin helps care workers support clients’ well-being. Effective support depends on recognising the importance of nutrition, hydration, hygiene, and gentle care. Regular checks and early action support the skin’s natural functions and help prevent problems.