Short answers( Just few words) Basic bio, answer them all and I will rate you 1-

Question

Short answers( Just few words) Basic bio, answer them all and I will rate you

1-What type of tissue is the epidermis? What germ layer is it derived from?

2-What does it mean that the epidermis is avascular? Virtually all cells of the human body are within 20 µm of a capillary. Do some of the cells of the epidermis fly in the face of this general rule?

3-Epidermal ridges and dermal papillae increase the surface area for attachment of the epidermis to the dermis. What are the structures that lag the epidermis down to the dermis?

4-What is the most apical stratum of the epidermis? Visceral? Which layer is not present in thick skin?

5-Thick skin has five strata and thin has four, but this is not the primary reason why thick skin is so much thicker than thin skin. What is the primary reason?

6-What is the most abundant cell in the epidermis of your skin? What other cells are located in the epidermis? In which stratum are the cells you identified located?

7-How long does it take a keratinocyte produced in the stratum germinativum to be sloughed off the surface of the epidermis?

Explanation / Answer

Ques-1: 1-What type of tissue is the epidermis? What germ layer is it derived from?

Answer:

The epidermal tissue is composed of keratinized, stratified squamous epithelium. This tissue has derived from ectoderm developing embrymic germ layer.

Ques- 3-Epidermal ridges and dermal papillae increase the surface area for attachment of the epidermis to the dermis. What are the structures that lag the epidermis down to the dermis?

Skin structure:

Skin, in association with its accessory structures and subcutaneous tissue consists of the “integumentary system.” This system protects the internal organs from the external environment and hazards. This system also helps to maintain the body temperature by resisting loss of temperature. The accessory structure of skin includes the receptors, glands, hair and nails. The integumentary system enables synthesizing vitamin D from natural sunrays and using adipose tissue; thermoregulation & hydroregulation. It has sensory nerve innervations for perception and sensation to external communication stimuli.

The three layers of skin are,

1). Epidermis; 2 . Dermis; 3. Hypodermis

Epidermis is the outermost layer of the skin made of keratinized stratified squamous epithelial tissue in which outer or apical surface cells are hardened or dead. It does not contain blood vessels (not vascularized), and the dermal layer supplies oxygen and nutrients by means of diffusion. The layer of the epidermis that contains transulacent cells filled keratin are often referred as “thick stratum lucidum”. The other layers often sloughed off from the surface composed of dead cells that are flat and filled with keratin often referred as “stratum corneum”. The epidermis has a stratified squamous epithelium, which normally undergoes ecdysis or moulting & do not require nutritious supply so that there no blood supply that extends into the epidermis.

The layer of skin arranged in between the epidermis and hypodermis (subcutaneous tissue) known as dermis. Dermis contains the roots of hair cells, sweat glands, sebaceous glands, blood vessels and receptors of mechanical stimuli. The dermis consists of two regions,

1). Papillary region (made of loose areolar connective tissue)

2). Reticular region (made of dense irregular connective tissue)

The major function of dermis is to cushion the body from mechanical stress and provide elastic nature to the skin, the presence of sensory receptors also provide the sense of touch and heat.

Hypodermis is the connective tissue present beneath the skin and is made of adipose and areolar (loose connective tissue). This layer insulate the body to prevent the loss of heat an also act as an energy reservoir in the form of adipose tissue.

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