Human Skin Structure and Types

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Questions and Answers

What is the heaviest organ in the human body?

Heart

Liver

Brain

Skin (correct)

What is the primary function of the Stratum Germinativum layer of the epidermis?

Pigment production

Barrier function against external factors

Constant production of epidermal cells (correct)

Protection against UV radiation

Which type of skin covers the majority of the human body?

Stratified squamous epithelium

Thick skin

Keratinized epithelium

Thin skin (correct)

Which of the following cells is responsible for producing pigment in the epidermis?

Melanocytes (C) Signup and view all the answers

What is the characteristic of the Stratum Corneum layer of the epidermis?

Horny layer (D) Signup and view all the answers

What is the primary function of the Hypodermis layer of the skin?

Binding skin loosely to the underlying tissues (A) Signup and view all the answers

What is the characteristic of the dermis layer of the skin?

Thick and vascular (B) Signup and view all the answers

How often is the human epidermis renewed?

Every 15-30 days (A) Signup and view all the answers

What is the primary function of the lamellar granules in the stratum granulosum?

To produce sheets that envelop the cells and form a barrier against water loss (B) Signup and view all the answers

Which of the following characteristics is NOT a feature of the cells in the stratum spinosum?

Membrane-bounded lamellar granules (D) Signup and view all the answers

What is the main component of the cytoplasm in the stratum corneum?

Densely packed keratin filaments (D) Signup and view all the answers

Which of the following factors does NOT contribute to the color of the skin?

Keratin filaments in the stratum corneum (B) Signup and view all the answers

What is the purpose of the epidermal barrier formed by the lipid-rich material in the stratum granulosum?

To protect the skin from water loss and penetration by foreign materials (A) Signup and view all the answers

What is the primary function of melanocytes in the epidermis?

To synthesize melanin and store it in melanosomes (B) Signup and view all the answers

Which of the following layers is NOT present in thin skin?

Stratum lucidum (B) Signup and view all the answers

What is the characteristic of the cells in the stratum corneum?

They are non-nucleated and have a cytoplasm filled with filamentous keratins (D) Signup and view all the answers

Study Notes

Skin Overview

Skin is the heaviest and largest organ in the human body, making up 15-20% of total body weight.
There are two types of skin: thick skin (found on palms and soles) and thin skin (found on the rest of the body).

Layers of the Skin

The skin consists of two distinct regions: epidermis (outer) and dermis (inner).
Epidermis:
- Thin
- Derived from ectoderm
- Non-vascular but rich in sensory nerve endings
Dermis:
- Thick
- Derived from mesoderm
- Characterized by connective tissue, vascular, and nerves

Hypodermis

Beneath the dermis lies the hypodermis, a loose connective tissue that may contain pads of adipocytes.
Hypodermis binds skin loosely to the underlying tissues.

Epidermal Cells

Keratinocytes: most abundant cells in the epidermis
Non-keratinocytes:
- Melanocytes: pigment-producing cells
- Langerhans cells: antigen-presenting cells
- Merkel cells: tactile epithelial cells

Stratum Corneum (Horny Layer)

Composed of 5 layers of keratinocytes
Keratinocytes in the stratum basale contain intermediate filaments composed of keratins
Function: renewal of keratinocytes

Other Epidermal Layers

Stratum Spinosum (prickle cell layer):
- Cells have short cellular extensions around the tonofibrils
- Appearances of many short spines or prickles at the cell surfaces
Stratum Granulosum (granular layer):
- Cells have keratohyaline granules and lamellar granules
- Contains lipids that produce sheets that envelop the cells
Stratum Lucidum (clear zone):
- Only seen in thick skin
- Cells have flattened nuclei and are degenerating
- Cytoplasm consists almost only of densely packed keratin filaments

Melanocytes

Depend on the interaction of three factors:
- Melanin: yellow to brown to black pigment produced by melanocytes
- Carotene: orange-yellow pigment found in some vegetables
- Hemoglobin: red coloring from blood cells in dermis capillaries
Melanocytes:
- Specialized cells of the epidermis found among the cells of stratum basale and in the hair follicles
- Synthesize melanin from tyrosine and store it in vesicles called melanosomes

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Description

Learn about the human skin, its composition, and its different layers. Understand the characteristics of thick and thin skin, as well as the epidermis and dermis regions.