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Cells lining the hair follicle are like shingles facing in the opposite direction. They interlock with the scales of the hair cuticle and resist pulling on the hair. When a hair is pulled out, this layer of follicle cells comes with it. It consists of several layers of elongated keratinized cells that appear cuboidal to flattened in cross sections.
Anatomy and Physiology of Hair
You will see a glassy membrane in the diagram that separates the inner root layer from the outer root layer. The hair bulb represents the hair matrix, and hair follicles stem cells. These hair matrices and stem cells are responsible for forming the hair. The stem cells proliferate, move upwards, and gradually become keratinized to produce the hair. The outer root layer of the hair follicle is continuous with the epidermis. You will find a glassy basement membrane that separates this outer root layer from the surrounding connective tissue.
Beneath the skin of keratin
You will also find more oval structures in the shaft of cattle or goat hair than in humans. It is very easy to visualize the scales and medulla of a hair shaft. Simply, you should follow a simple procedure and need some instruments. You will find the uniserial, multiserial ladder, vacuolated, and lattice medulla in different animal species.
How to get rid of uneven skin tone
Again, the diagram shows the cortex layer just deep into the cuticle layer. The medulla of the hair is the core, which is also shown in this diagram. In addition, you will understand the medulla feature clearly from the next labeled diagram.
Without enough niacin, follicles may not produce hair efficiently. The sebaceous gland produces sebum, or oil, which is the body’s natural conditioner. More sebum is produced during puberty, which is why acne is common during the teen years. It protects your skin and traps particles like dust around your eyes and ears. If your hair gets damaged, it can renew itself without scarring. The medulla of the dog hair is generally continuous, but it may be vacuolated to amorphous and occasionally very broad.
The cuticle is composed of multiple layers of very thin, scaly cells that overlap each other like roof shingles with their free edges directed upward. The density of hair does not differ much from one person to another or even between the sexes; indeed, it is virtually the same in humans, chimpanzees, and gorillas. Differences in apparent hairiness are due mainly to differences in texture and pigmentation. And this, of course, only adds to the complexity thispuzzling type of hair loss presents. You can help keep your hair healthy by taking care of your overall health.
Basic Hair Structure and function
You will find two main parts in hair – a cylindrical shaft and a terminal hair follicle. This article might help you to know the different features of a hair (shaft and follicle) under a light microscope with their concise description. Again, I will try to show you the hairs of different animals like rabbits, cats, and dogs with their specific features. The hair follicle serves as a reservoir for epithelial and melanocyte stem cells and it is capable of being one of the few immune privileged sites of human body.
Hair Shaft
Here, it shows the different epidermis layers and dermis of animal skin with a hair shaft and follicle. The contraction of the arrector pili muscle pressed upon the sebaceous gland helps them secret within the hair follicle. You will quickly identify and differentiate the animal hair from human hair under a light microscope with the help of their cuticle and medulla features. Generally, the animal hair contains a continuous or stacked medulla in its hair shaft. You will learn more about the microscopic features of the sebaceous glands of the hair follicle in the next section of this article. Sebaceous are the branched acinar holocrine glands that attach to the hair follicle.
The hair follicle becomes almost verticle relative to the skin surface of any animal. Again, the skin surface overlying the attachment of the arrector pili muscle becomes depressed while the surrounding area becomes raised. Fine, let’s know some of the important microscopic features of these two structures (sebaceous gland and arrector pili muscle) from the skin histology slide.
The hair shaft is the visible, nongrowing portion of a hair protruding from the skin. In contrast to the continuous melanogenesis observed in epidermal melanocytes, follicular melanogenesis is a cyclic phenomenon. It is ceased in early the anagen-catagen transition, restarted with the down-regulation of key enzymes of melanogenesis, followed by hair follicle melanocyte apoptosis. The hair follicle is one of the characteristic features of mammals serves as a unique miniorgan (Figure 1).
At the base of the hair bulb, the germinatinglayer merges into the outer root sheath(which forms the inner wall of the follicle). Hair is continually shed and renewed by the operation of alternating cycles of growth, rest, fallout, and renewed growth. The average life of different varieties of hair varies from about four months for downy hairs to three to five years for long scalp hairs. Now, let’s see the second diagram (schematic presentation), where the different layers of the hair follicle are seen.
You may determine the hair from the different parts of the animal’s body. The length, shape, size, color, stiffness, curliness, and microscopic features might help you to identify the hairs from the different body areas. Sometimes sebaceous gland occurs independently in the hair follicle and directly opens on the skin surface. The lipid of these inner cells is discharged by the disintegration of the innermost cells that are replaced by the proliferation of the outer cells. You will find the oily secretion from the sebaceous gland of any animal that helps to keep the skin and hair soft. Sometimes, a microscopic view shows the great mitotic activities of the hair root and bulb cells.
In hair follicles, 5-alpha reductase is found in the sebaceous glands, dermal papilla, inner root sheath and outer root sheath (2). And androgen receptor sites are found in dermal papilla cells and sebaceous glands (3). Again, the hair matrix stem cells help form the inner and outer root layer of the hair follicle. There is a dermal papilla at the base of the hair bulb and remains in the skin’s dermis. Hair texture (straight, curly) is determined by the shape and structure of the cortex, and to the extent that it is present, the medulla. The shape and structure of these layers are, in turn, determined by the shape of the hair follicle.
Medulla is located in the center of the hair shaft preferably presented in coarser fibers. The outer covering of the hair shaft, the cuticle, is the protective outer layer of the hair. It is made up of cells that tile over each other partially overlapping. This is what both protects the cortex and holds the rope like cells together. A healthy cuticle layer is what gives hair its natural shiny appearance.
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