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Hair Follicle
We are familiar with only the top portion of hair which extends from the skin. This is known as the hair shaft. Below the skin, the shaft becomes the hair root which connects to the hair bulb. At the base of the hair bulb is a structure called a hair papilla that contains connective tissue and capillaries that feed the living cells in the hair bulb. At the top of the hair bulb are a group of mitotic cells that are constantly producing new hair cells and causing the hair to grow. Melanocytes are also found in the hair bulb. Depending on the combination and amount of pigments being made, hair can range from a light blond color to a dark red or black color.
Each hair is surrounded by a structure known as a hair follicle which begins as invagination of the epidermis and covers the hair. The hair is in the follicle is surrounded by a root sheath that is made up of 3 sublayers. The arrector pili is attached to the root sheath and serve to make the hair stand erect in response to the sympathetic stimuli; the result giving you goose bumps. At the bottom of the follicle are numerous nerve endings, which make hair an effective sensory receptor.
The hair itself has 3 layers to it. The middle layer is called the medulla and is absent in vellus hair. When present, in terminal hair, it contains a "soft" form of keratin and air spaces. Surrounding the medulla is the cortex. This layer accumulates melanin and depending on the amount of melanin and the ratio of eumelanin to pheomelanin makes the hair anywhere from black to red to blonde. The outer cuticle contains flattened cells containing a hard tough form of keratin.
Slides on this page were made by students between the spring of 2018 and the spring of 2020. Go through
the diffrent student pictures and compare them to your lab book picture. Then slect one to draw on paper.
Label the different structures.These slides are from the scalp. Therefore, there are numerous eccrine sweat glands and Sebaceous glands.
so draw and label those too.
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Student Images |
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