The Roots of Plants
The roots of hair are made up of several different structures, cells, and nerves. Here, we will discuss the growth cycle and receptors, as well as a little about the hair follicle. The hair follicle is a tiny structure attached to a tiny muscle, called the arrector pili, which makes your hair stand up. It has several nerves that terminate at the end of the hair follicle. The follicle has many sensitive receptors that detect the slightest draft. The hair root is rounded, and the papilla is what supplies blood and nutrients to the bulb. New hair cells are continually created in the bulb, which consists of a small tube.
Cells
The cells of hair root are highly specialized to allow the plant to absorb more water and minerals. This is because they are found underground and do not have chloroplasts, a type of cell that requires light for photosynthesis. Instead, these cells have long projections, which increase the surface area for absorption. The study of hair root cells will help scientists understand how these plants process environmental stress and how they respond to it. For more information, visit the Seneca Institute.
The first method of isolating root hair cells maximizes purification but provides a low yield and is labor intensive. However, the second method can be used to grow large numbers of root hair cells and is compatible with -omic analyses. The updated method is highly reproducible, yielding high-quality isolated root hair cells. The second method offers high-quality root hair cells but can result in contamination with non-hair cells during the cultivation process.
Structures
Hair follicles are made up of multiple layers of cells ranging from a single strand to a bulb. The follicle is continuous with the superficial epidermis, but extends into the dermis. The follicle is surrounded by a thick, concentric sheath called a matrix. This sheath contains cells with various differentiation states that are the source of the cellular types of the follicle. A single strand of hair is composed of many layers, including three concentric layers. The outermost layer of the matrix is a 3.5 to 4.5-um-thick cuticle. These cells are mitotically active and provide protection to the basal layers.
The hair root is composed of five main structures. Each structure has a distinct function and contributes to a particular characteristic. The first layer is the cuticle, which is composed of shingle-like cells that function defensively to prevent the inner structure of the follicle from being damaged. The second layer is the cortex, which provides strength, color, and texture to the hair fiber. The final layer is called the medulla, and is only present in large, thick hairs.
Growth cycle
The growth cycle of hair involves three phases. During the anagen phase, the cells in the root of the hair begin to divide and form new hair. This phase can last anywhere from a few weeks to two months, depending on your individual genetics and hair growth cycle. During this phase, the hair grows about half an inch every month or six inches per year, depending on your age and health. During this phase, your hair falls out more frequently than in other phases.
In the anagen phase, hair roots divide rapidly, adding to the hair shaft. During this phase, the hair grows approximately 1 centimeter per 28 days and stays in the anagen phase for two to seven years. The growth cycle of hair is genetically determined, but there is no known trigger for the hair to enter the catagen phase. In the final resting phase, the hair roots die and new hair cells begin to multiply at the base of the “empty” hair follicle.
Receptors
Receptors in hair root are nerve endings that sense motion and amplitude of a stimulus. They are responsible for detecting hot and cold, as well as light and motion. Some hair follicle receptors are highly sensitive to movement, while others are slow-adapting. Receptors in hair root differ in sensitivity based on their location. Some hair follicle receptors detect deflection of the skin, while others detect high-frequency vibration.
The follicle is enclosed within a protective casing called the hair shaft. The follicular nerve ends are surrounded by flower-spray endings that act as basic somatosensory receptors. The follicular nerves then stimulate muscle fibers and cause piloerection. They can also respond to touch, pain, and vibration. This is why hair follicles produce so much hair.
Arrector pili muscle
The arrector pili muscle is a small group of smooth muscles that attach to the hair follicle. It functions to pull hair shafts perpendicular to the skin. These muscles are triggered by nerve endings in the sympathetic system, and when they contract, they cause hairs to stand on end. During periods of stress, these muscles can be triggered to contract, which results in goosebumps and goose bumps.
The arrector pili muscle is connected to each hair follicle. As it contracts in response to nerve signals from the sympathetic nervous system, it causes the external hair shaft to “stand up,” trapping a layer of air. This process is similar to what creates goose bumps on an animal’s fur. The goose bumps are more noticeable in animals with thicker coats. Moreover, they may be responsible for hair loss.