3.1 Cells, tissues, skin & body systems for cosmetology
Key Takeaways
- A cell is the basic unit of all living things; its protoplasm contains a nucleus that controls reproduction, cytoplasm that carries food, and a cell membrane that regulates what enters and leaves.
- Metabolism has two phases that run at once: anabolism builds larger molecules and stores energy, while catabolism breaks molecules down and releases energy.
- The four types of tissue are connective, epithelial, muscular, and nerve (nervous) tissue, and each performs a distinct function in the body.
- The skin is the body's largest organ; the epidermis has five layers (corneum, lucidum, granulosum, spinosum, germinativum) over the dermis and subcutaneous adipose tissue.
- Massage movements are generally directed from a muscle's insertion toward its origin; the fifth cranial nerve is the chief sensory nerve of the face and the seventh is the chief motor nerve.
The Cell — the Basic Unit of the Body
Everything a cosmetologist touches — skin, hair, nails, and the muscles worked during a massage — is built from cells, so licensing exams open the science unit here. A cell is the basic unit of all living things. Most cells contain protoplasm, a colorless, jelly-like substance in which food elements such as proteins, carbohydrates, fats, mineral salts, and water are present. Inside the protoplasm are three structures you must know:
- Nucleus — the dense center that controls reproduction and the cell's other activities; it holds most of the cell's genetic material.
- Cytoplasm — the watery fluid outside the nucleus that carries the food needed for growth, reproduction, and self-repair.
- Cell membrane — the outer wall that encloses the cytoplasm and lets soluble substances pass into and out of the cell.
Cell Reproduction and Metabolism
As long as cells receive food, water, and oxygen and can remove waste, they grow and reproduce. Most body cells reproduce by mitosis, dividing to form two identical daughter cells. Metabolism is the chemical process that keeps cells alive, and it has two phases you must be able to tell apart. Anabolism is constructive metabolism — small molecules are built into larger ones and energy is stored. Catabolism is destructive metabolism — larger molecules are broken into smaller ones and energy is released to do work such as muscle contraction. The two phases run at the same time and stay balanced in a healthy body.
The Four Types of Tissue
A tissue is a group of similar cells that carries out a particular job. Cosmetology theory recognizes four main types:
| Tissue type | Function and where it is found |
|---|---|
| Connective | Supports, protects, and binds other tissues — bone, cartilage, tendons, ligaments, fat (adipose), and blood |
| Epithelial | A protective covering on body surfaces — skin, mucous membranes, glands, and the linings of the heart and digestive and respiratory organs |
| Muscular | Contracts and moves the parts of the body |
| Nerve (nervous) | Carries messages to and from the brain and coordinates body functions |
The Skin
The skin is the body's largest organ. It has two main divisions: the epidermis (the outer layer, which has no blood vessels) and the dermis (the inner, "true" skin). From the surface inward, the epidermis has five layers — stratum corneum (the horny, shedding outer layer), stratum lucidum (a clear layer, thickest on the palms and soles), stratum granulosum (the granular layer), stratum spinosum (the spiny layer), and stratum germinativum, or basal layer, where new cells and the pigment melanin are formed. The dermis holds the papillary and reticular layers, containing blood vessels, nerves, hair follicles, and arrector pili muscles, along with two important glands: the sudoriferous (sweat) glands, which regulate temperature and excrete waste, and the sebaceous (oil) glands, which produce sebum to lubricate the skin and hair. Beneath the dermis lies the subcutaneous (adipose) tissue, which gives smoothness and contour, stores energy, and cushions the body. The skin's main functions are easy to recall as protection, sensation, heat regulation, excretion, secretion, and absorption.
Body Systems Cosmetologists Use Every Day
Skeletal and Muscular Systems
The skeletal system is the physical foundation of the body. The skull is made of the cranium (8 bones) and the facial skeleton (14 bones); the neck includes the cervical vertebrae and the hyoid bone; and the arm and hand include the humerus, ulna, radius, carpus (wrist), metacarpus (palm), and phalanges (fingers). Knowing these lets you describe where you are working during scalp and hand services.
The muscular system covers, shapes, and supports the skeleton. Because cosmetologists knead and stimulate muscles during scalp, facial, and hand massage, you must know the muscles of the head, face, and neck: the epicranius (occipitofrontalis) of the scalp, the orbicularis oculi and orbicularis oris around the eyes and mouth, the buccinator of the cheek, the masseter and temporalis used in chewing, the zygomaticus, the platysma, and the sternocleidomastoid of the neck. Every muscle has an origin (its fixed attachment) and an insertion (its movable attachment). As a rule, massage movements are directed from the insertion toward the origin to avoid damaging muscle tissue.
Nervous and Circulatory Systems
The nervous system controls and coordinates every other system. Nerves are sensory (afferent — they carry impulses such as touch, cold, heat, and pressure to the brain), motor (efferent — they carry impulses to the muscles), or mixed. The two most important facial nerves are the fifth cranial nerve (trifacial, or trigeminal), the chief sensory nerve of the face, and the seventh cranial nerve (facial), the chief motor nerve of the face and the muscles of expression. The eleventh cranial nerve (accessory) controls the muscles of the neck and back, which matters during neck and shoulder massage.
The circulatory (cardiovascular) system moves blood through the body by way of the heart, arteries, capillaries, and veins, while the lymphatic system carries lymph. The common carotid arteries are the main source of blood to the head, face, and neck, and the jugular veins return it. Blood supplies oxygen and nutrients, removes waste and carbon dioxide, and helps regulate body temperature — which is exactly why gentle massage improves the color, nourishment, and elimination of the skin.
Which phase of metabolism builds larger molecules from smaller ones and stores energy?
Which type of tissue supports, protects, and binds together other tissues, including bone, cartilage, fat, and blood?
During massage, movements are generally directed from a muscle's insertion toward its: