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Hair color

Similar to the skin, hair gets its color from the pigment melanin, produced by melanocytes in the hair papilla. Different hair color results from differences in the type of melanin, which is genetically determined. As a person ages, the melanin production decreases, and hair tends to lose its color and becomes gray and/or white.

Nails

The nail bed is a specialized structure of the epidermis that is found at the tips of our fingers and toes. The nail body    is formed on the nail bed    , and protects the tips of our fingers and toes as they are the farthest extremities and the parts of the body that experience the maximum mechanical stress ( [link] ). In addition, the nail body forms a back-support for picking up small objects with the fingers. The nail body is composed of densely packed dead keratinocytes. The epidermis in this part of the body has evolved a specialized structure upon which nails can form. The nail body forms at the nail root    , which has a matrix of proliferating cells from the stratum basale that enables the nail to grow continuously. The lateral nail fold    overlaps the nail on the sides, helping to anchor the nail body. The nail fold that meets the proximal end of the nail body forms the nail cuticle    , also called the eponychium    . The nail bed is rich in blood vessels, making it appear pink, except at the base, where a thick layer of epithelium over the nail matrix forms a crescent-shaped region called the lunula    (the “little moon”). The area beneath the free edge of the nail, furthest from the cuticle, is called the hyponychium    . It consists of a thickened layer of stratum corneum.

Nails

These two images show anatomy of the fingernail region. The top image shows a dorsal view of a finger. The proximal nail fold is the part underneath where the skin of the finger connects with the edge of the nail. The eponychium is a thin, pink layer between the white proximal edge of the nail (the lunula), and the edge of the finger skin. The lunula appears as a crescent-shaped white area at the proximal edge of the pink-shaded nail. The lateral nail folds are where the sides of the nail contact the finger skin. The distal edge of the nail is white and is called the free edge. An arrow indicates that the nail grows distally out from the proximal nail fold. The lower image shows a lateral view of the nail bed anatomy. In this view, one can see how the edge of the nail is located just proximal to the nail fold. This end of the nail, from which the nail grows, is called the nail root.
The nail is an accessory structure of the integumentary system.

Nails are accessory structures of the integumentary system. Visit this link to learn more about the origin and growth of fingernails.

Sweat glands

When the body becomes warm, sudoriferous glands produce sweat to cool the body. Sweat glands develop from epidermal projections into the dermis and are classified as merocrine glands; that is, the secretions are excreted by exocytosis through a duct without affecting the cells of the gland. There are two types of sweat glands, each secreting slightly different products.

An eccrine sweat gland    is type of gland that produces a hypotonic sweat for thermoregulation. These glands are found all over the skin’s surface, but are especially abundant on the palms of the hand, the soles of the feet, and the forehead ( [link] ). They are coiled glands lying deep in the dermis, with the duct rising up to a pore on the skin surface, where the sweat is released. This type of sweat, released by exocytosis, is hypotonic and composed mostly of water, with some salt, antibodies, traces of metabolic waste, and dermicidin, an antimicrobial peptide. Eccrine glands are a primary component of thermoregulation in humans and thus help to maintain homeostasis.

Eccrine gland

This diagram shows an eccrine sweat gland embedded in a cross section of skin tissue. The eccrine sweat gland is a bundle of white tubes embedded in the dermis. A single white tube travels up from the bundle and opens on to the surface of the epidermis. The opening is called a pore. There are several pores on the small block of skin portrayed in this diagram.
Eccrine glands are coiled glands in the dermis that release sweat that is mostly water.

An apocrine sweat gland    is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions. Apocrine sweat glands are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle. In addition to water and salts, apocrine sweat includes organic compounds that make the sweat thicker and subject to bacterial decomposition and subsequent smell. The release of this sweat is under both nervous and hormonal control, and plays a role in the poorly understood human pheromone response. Most commercial antiperspirants use an aluminum-based compound as their primary active ingredient to stop sweat. When the antiperspirant enters the sweat gland duct, the aluminum-based compounds precipitate due to a change in pH and form a physical block in the duct, which prevents sweat from coming out of the pore.

Sweating regulates body temperature. The composition of the sweat determines whether body odor is a byproduct of sweating. Visit this link to learn more about sweating and body odor.

Sebaceous glands

A sebaceous gland    is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands are associated with hair follicles. They generate and excrete sebum    , a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable. The fatty acids of sebum also have antibacterial properties, and prevent water loss from the skin in low-humidity environments. The secretion of sebum is stimulated by hormones, many of which do not become active until puberty. Thus, sebaceous glands are relatively inactive during childhood.

Chapter review

Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. Hair is made of dead keratinized cells, and gets its color from melanin pigments. Nails, also made of dead keratinized cells, protect the extremities of our fingers and toes from mechanical damage. Sweat glands and sebaceous glands produce sweat and sebum, respectively. Each of these fluids has a role to play in maintaining homeostasis. Sweat cools the body surface when it gets overheated and helps excrete small amounts of metabolic waste. Sebum acts as a natural moisturizer and keeps the dead, flaky, outer keratin layer healthy.

Questions & Answers

Most body movement is involuntary (true or false)
Ruma Reply
true
Ashiish
True
Masud
I think true.......
Ihsan
true
odeh
true
Atul
true
Serhana
all of the following substance move in in and out of cell except
Mohd Reply
all of the following substance move in and out of cells except
Mohd
Which signaling molecule is most likely responsible for an increase in digestive activity?
Tonya Reply
Hi I think it is DNA
libim
Homeostatasis return to the body to a healthy state after a stressful stimuli by producing
Ofosu Reply
There are some people suffering serious injured what will we do in doing X-ray?
Jefford Reply
observe bone arrangements n associated structures like soft tissues muscles in general the radiographical changes
Terry
epithelial tissue lines blood vessels
Laura Reply
what is difference between anabolism and catabolism in simple language
Chinaza Reply
anabolism simply means building up while catabolism breaking down
Maaruf
building up and breaking down
odeh
explain respiratory centers
Tharshana Reply
which enzyme help in excretion of bile
Sakshi Reply
how conversion of Beta-carotiene into vitamin-A takes place
Sakshi
best reference books for anatomy pls suggest that
Sakshi
what is gross anatomy
Saroj Reply
The study of large structure of the body
Mablean
macroscopic anatomy (Gross anatomy)
odeh
manipulation of structures without aid of microscope due to their size
libim
what is scrotum
Dakshit Reply
a bag of skin near the penis which contains the testicles
Mablean
hi
Sardar
its me Sardar from kpk pakistan
Sardar
Why are you on my digits
Mablean
hi
Kryme
it is part if male organ that hold testis in position it also regulates temperature
libim
how does it work?
Uriah Reply
I want to know the fertilization process in human
Nana Reply
Which plane divides the body into right and left parts
Kaeze
sagittal plane
Irvin
Thank you
Kaeze
Homestatic regulations usually involves a (n) _ that detects a particular stimulus, and a(n) _that respond to the stimulus by communicating with a (n) _whose activity has an effect on the same stimulus.
Kaeze
A cell is producing proteins to be transported out of that cell. They will be processed on ribosomes that are
Kaeze
what are diseases in the bood
Azoyenime Reply
Haemophilia
Aliyu
right hypochondriac rision how meain word
Ganesh Reply
Diabetes insipidus or diabetes mellitus would most likely be indicated by ________.
Ganesh
what are the three types of blood stem and explanation how they form in steps
Henry Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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