Hair accessory structures Flashcards
Regarding hair (pili), discuss the location of hair on the body, and give a brief description of a handful of roles of pili.
Hair only grows on thin skin, skin lacking stratum lucidum. The role of pili is to protect the scalp from UV radiation, insulate against heat loss, and prevent foreign objects from entering the body.
Name the parts of hair, the location of each part, cells & tissue composition of each.
The hair is made of three parts: the shaft, the root, and the follicle. The shaft is part of the hair above the skin surface and it’s composed of overlapping dead keratinized epidermal cells. The root is a deep extension of the shaft that penetrates into the dermis. The follicle is below the level of the skin and surrounds the hair root. It’s innervated and vascularized.
The shaft and root are composed of 3 parts: the outer cuticle, middle cortex, and inner medulla. The cuticle is made of dead, keratinized epidermal cells. The cortex is the bulk of the shaft and root. The medulla contains melanin that gives the hair color.
Outside of the medulla, cortex, and cuticle, there is an epithelial root sheath(follicle) and dermal sheath. The epithelial root sheath has an internal and external root. The internal root sheath is a sheet of epithelial cells produced by stem cells(hair matrix). The external root sheath is a downward invagination of the epidermis. The dermal root sheath is a covering of dense irregular connective tissue continuous with the dermis.
The bulb of the hair contains the papilla of the hair which contains capillaries that nourished the hair matrix and has mitotically active cells that are responsible for hair growth.
For both the hair shaft & the follicle, name the layers of each superficial to deep
Hair shaft:
Outer Cuticle
Middle Cortex
Inner medulla
The follicle:
Dermal root sheath
Epithelial root sheath (external root sheath, internal root sheath)
Locate the cells that give hair its color.
Melanocytes in the medulla, which contain pigment granules-melanin
Describe the location, structures & function of the hair bulb, including the papilla of the hair.
The hair bulb is at the very bottom of the hair and contains an opening at the base of the hair follicle called the papilla of the hair. The papilla of the hair contains capillaries that nourish the hair matrix. The metabolically active cells grow hair whenever it’s cut.
Discuss the role of melanocytes & hair matrix cells, as well as the innervation & vascularization of the papilla of the hair
Hair matrix cells grow hair after its cut. Melanocytes give the hair color. Capillaries are found in the papilla of the hair to give nutrients to the hair. The hair root plexus is a bundle of nerves that respond to any displacement or movement of the hair follicle
Locate and give the function of the arrector pili & the hair root plexus, including the type of tissue of each.
Arrector pili(muscular tissue) = connects the hair follicle to the connective tissue of the basement membrane
Hair root plexus(nervous tissue)= responds to any displacement or movement of the hair follicle
Name the 3 types of hair & be able to name them in ontogenetic order & briefly discuss the transitions between the 3 types.
Three types of hair in ontogenetic order are lanugo, vellus, and terminal. Lanugo hair is present in the body of the fetus. Before the birth of the fetus, hairs on the scalp, eyebrows, and eyelashes transform from lanugo to terminal hairs. The rest of the hair on the fetus’s body turns into vellus hair. When reaching puberty, the vellus hairs transform into terminal hairs.
Contrast apocrine sweat glands with eccrine sweat glands, focusing on location, type of tissue, type of exocrine gland, type of secretion, secretory location, the role of the secretion, and timing of Secretion!
Apocrine Sweat Gland
- The skin of the axilla, groin, areolae, and bearded facial regions of adult males
- Begins function after puberty
- Secretes slightly viscous sweat
- Secrete by merocrine mechanisms
- Secretory portion deep in the dermis
Eccrine Sweat gland
- Forehead, palms, and soles
- The most numerous
- Secretes watery solution
- Secretory portion deep in the dermis or subcutaneous layer
Briefly describe the location & secretion of ceruminous glands
Ceruminous glands are modified sweat glands located in the ear canal. They, with the help of nearby sebaceous glands, produce ear wax(cerumen) which provides a sticky barrier that prevents entry of foreign objects
Briefly describe the location & role of the nail body, root, hyponychium, bed & eponychium
The nail body= provides counter pressure to the epidermal ridges of the fingertips to improve touch, graph, coordination, and manipulation
root= produces most of the volume of the nail and the nail bed
Hyponychium=attaches the very distal edge of the nail body to the skin of the fingertips
Bed= protection and sensation
Eponychium= a bond of stratum corneum that adheres to the proximal edge of the nail bed
Describe sebaceous glands, focusing on location, type of tissue, type of exocrine gland, type of secretion, secretory location, and role of the secretion.
Sebaceous glands are simple branched acinar glands. They secrete using holocrine secretion, where the entire cell ruptures secreting the entire contents of the cell after the product accumulates. Starting from the stratified cuboidal glandular epithelium cells, oil is secreted into the lumen of the gland. From there, the sweat travels to the duct of the gland, then onto a hair follicle, which migrates superficially into the covering epithelium.
Describe eccrine sweat glands, focusing on location, type of tissue, type of exocrine gland, type of secretion, secretory location, and role of the secretion (particularly the details of evaporative cooling mechanisms)
Eccrine sweat glands are sudoriferous glands, meaning they are simple coiled tubular glands. In eccrine sweat glands, the glandular epithelium of the secretory portion is made of simple cuboidal cells. Starting from the glandular epithelium, sweat is secreted through merocrine secretion, using standard exocytosis, into the lumen of the gland. From there, the sweat travels to the duct of the gland, then onto the epidermal covering, to serve its purpose of evaporative cooling.
