5.1 Cells, Tissues & Body Systems

Why Anatomy and Physiology Appear on Your Exam

The Tennessee cosmetology theory exam follows the PSI outline, and a meaningful share of its Safety and Infection Control domain is anatomy and physiology. Examiners are not testing you to medical depth — they want to confirm that you understand the living structures you touch every day: the skin you treat, the scalp you massage, the muscles and nerves beneath your hands during facial and neck services. Questions on this material tend to be direct definitional recall: what the nucleus does, what anabolism means, which tissue type covers the body. Learn the terms in this section precisely, because exam answer choices are often built from near-miss word pairs such as anabolism versus catabolism.

The Cell: Basic Unit of All Living Things

Cells are the basic units of all living things, from bacteria to plants to human beings. Every cell is made of protoplasm, a colorless, jelly-like substance in which the elements carbon, oxygen, hydrogen, and nitrogen are found. Three structures inside the cell are tested over and over:

• The nucleus is the dense, active protoplasm found in the center of the cell. It is the control center of the cell — it contains the genetic material (DNA) and controls cell reproduction and most cell activities.
• The cytoplasm is the protoplasm of the cell that surrounds the nucleus. This gel-like material holds the cell's internal structures and is where food is mineralized and where growth, reproduction, and metabolism take place.
• The cell membrane is the cell wall that encloses the protoplasm. It is semipermeable, meaning it permits soluble substances to enter and leave the cell while keeping other substances out.

Cells need food, oxygen, and water to survive and reproduce, and they must eliminate waste products. Mitosis is the process of cell division: the cell divides into two identical daughter cells, allowing tissue to grow and repair itself — the same process that lets skin heal after a scrape or a minor waxing irritation.

Metabolism is the set of chemical processes that take place in living organisms, through which the cells are nourished and carry out their activities. It has two phases, and the exam loves to ask you to tell them apart:

• Anabolism is constructive metabolism — the process of building up larger molecules from smaller ones. During anabolism the body builds tissue and stores energy, such as when amino acids are assembled into the keratin proteins of hair.
• Catabolism is destructive metabolism — the breaking down of complex compounds within the cells into smaller ones. This phase releases energy that has been stored, such as when stored nutrients are broken down to power muscle movement.

A memory aid that works: anabolism builds; catabolism cracks things broken down.

The Four Types of Tissue

A tissue is a collection of similar cells that perform a particular function. There are four basic types, and each one has salon-relevant examples:

Organs and the 11 Body Systems

Organs are structures composed of specialized tissues designed to perform specific functions in plants and animals. The skin is the largest organ of the body — a favorite exam fact. Organs working together to perform one or more functions make up a body system. There are 11 major systems:

1. Integumentary system — the skin and its accessory organs: hair, nails, and sweat and oil glands. This is the cosmetologist's home system.
2. Skeletal system — the physical foundation of the body, made of 206 bones in the adult, connected by movable and immovable joints.
3. Muscular system — covers, shapes, and supports the skeleton; it is made up of over 500 muscles, large and small, accounting for roughly one-third of body weight.
4. Nervous system — controls and coordinates all other systems; exceptionally well-organized, made of the brain, spinal cord, and nerves.
5. Circulatory system — controls the steady circulation of blood through the body by means of the heart and blood vessels; it has two divisions, the blood vascular system and the lymph vascular system.
6. Endocrine system — made of specialized glands that secrete hormones directly into the bloodstream, affecting the growth, development, and health of the entire body. Hormones strongly influence skin oiliness and hair growth patterns, which is why puberty, pregnancy, and thyroid conditions change what you see at the chair.
7. Digestive system — changes food into nutrients and waste; also called the gastrointestinal system.
8. Excretory system — purifies the body by eliminating waste matter; includes the kidneys, liver, skin, large intestine, and lungs.
9. Respiratory system — enables breathing, supplying the body with oxygen and eliminating carbon dioxide.
10. Lymphatic/immune system — made up of lymph, lymph nodes, and lymph vessels; it protects the body from disease by developing immunities and destroying disease-causing microorganisms.
11. Reproductive system — performs the process of reproduction.

How the Systems Interact in Salon Work

Body systems never work in isolation, and exam scenario questions reflect that. When you perform a scalp massage during a shampoo, you are acting on the muscular system directly, but you are also stimulating the circulatory system (increased blood flow brings nutrients to the hair papilla) and the nervous system (sensory nerves register the pressure, and the client relaxes). A client with an endocrine imbalance may present with sudden hair thinning — you do not diagnose, but you recognize the connection and refer appropriately. Understanding systems-level thinking is what separates a licensed professional from someone who has merely memorized techniques.

Exam tip: When a question asks which system a structure belongs to, anchor on the largest-organ fact (skin = integumentary), the 206-bone fact (skeletal), and the 500-plus-muscles fact (muscular). Those three numbers resolve a large share of systems questions.