i want 25 mutiple choice questions with their model answer below each question that covers different aspects of all the following information : Skin AppendagesThey include:1. Hair & hair follicle. 2. Sweat glands.3. Sebaceous glands. 4. Arrector pili muscles.The Hair- It consists of:a- Shaft: projecting above the surface of the skin.b- Root: embedded into the skin and consists of:1- Inner medulla: polyhedral cells with no pigments and contains soft keratin.2- Middle cortex: elongated cells with melanin pigments which give the color of the hair and contains hard keratin.3- Outer cuticle: flat cells containing hard keratin.c- Bulb: the expanded lower end of the hair responsible of its elongation.d- Hair follicle:* It is a tubular sheath formed by an epidermal down growth in which the root of the hair is present. * The wall of the hair follicle is called root sheath which is divided into 3 types:1- Inner root sheath: formed of 3 layers from inside outwards:a) Cuticle: flat scales containing soft keratin.b) Huxley’s layer: formed of 1-3 layers of cubicalcells.c) Henle’s layer: formed of one layer of elongatednon-nucleated cells.2- Outer root sheath: it is identical with the malpighian layer of the epidermis.3- C.T sheath: it is considered part of C.T. of the dermis and separated from the outer root sheath by a glassy membrane.The Sweat glandsThey are present deep in the dermis. They are simple coiled tubular glands. They are two types1 - Eccrine sweat glands:They are abundant throughout the dermis of both thick and thin skin.Highest concentration in the palms, soles, forehead. Formed of secretory portion and excretory ductsA- Secretory portion:Located in deep dermis, Lined by 2 types of cells: a) Dark cells: Pyramidal cells that line the lumen of the secretory portion, produce mucous secretion. b) Clear cells: Located between dark cells, release a watery secretion.B- Duct portion:Lined by stratified cuboidal epitheliumLeaves the secretory portion as a coiled duct, then becomes straight.Spirals through the epidermis to deliver sweat to the outside.2- Apocrine sweat glands:• It differ from the ordinary eccrine sweat glands in the following:Open into the upper part of hair follicles above the entrance of the sebaceous duct.Located in axilla, areola, peri-anal and pubic regionsThey secrete after puberty (Due to the effect of sex hormones).Despite their name, apocrine they are merocrine glands.The Sebaceous glandsSimple or branched alveolar glands. It is a holocrine gland.Present over most of the body surface except palms and soles.Most numerous and most productive on scalp, face and upper back.Controlled by androgen hormone.Formed of:A- Secretory portion:• Formed of acini embedded in the dermis.• The acinus is formed of larger cells filled with lipid vacuoles which degenerate to form an oily product called sebum.• Sebum is discharged into the sebaceous duct, which opens into the upper part of the hair follicle.• Sebum acts as cream that helps to keep skin soft preventing its cracking.B- Duct portion: is lined by stratified squamous epithelium.The Arrector pili muscles• Also known as hair erector muscles, they are smallmuscles attached to hair follicles.• Contraction of these muscles causes the hairs to bein erect position (standing).• Each arrector pili is composed of a bundle ofsmooth muscle fibers