Integumentary system

Human Anatomy

Assistant lecturer. Sawsan S. Hameed

Biology department

TIU

2021-2022

Outlines of the chapter

The integumentary system includes the skin, hair, oil and sweat glands, nails, and sensory receptors.

Thus, this chapter covers the following topics;

Functions of the integumentary system

Structure of the Skin and Subcutaneous tissue

Skin derivatives

Objectives of this lecture

You should be able to describe the following;

Functions of the integumentary system

Structure of the Skin

The layers of the skin

The difference between the integument layers

Introduction to integumentary system

The integumentary system consists of skin and its derivatives

The skin, or integument, is the body’s largest organ

4.5–5 kg (10–11 lb)

7%

It consists of three major layers:

1) Stratified squamous epithelium called the Epidermis

2) Deeper connective tissue layer called the Dermis.

3) Connective tissue layer, called the Hypodermis,

Introduction to integumentary

system

Protection; external conditions

Regulating of body temperature

Excretion and secretion

Generate vitamin D

Formation of new cells from stratum germinativum

Sensory function; touch, pressure, pain, heat, and cold

Maintenance of the body form & store water, fat and glucose

Functions of integumentary system

Skin structure

Dermis

Hypodermis

Epidermis

Integumentary System

The epidermis subdivided into the following strata or layers

• Stratum corneum

• Stratum lucidum

• Stratum granulosum

• Stratum spinosum

• Stratum basale or

germinativum

Epidermis

Epidermis

Derived from the ectoderm, it

consists of a keratinized

stratified squamous epithelium

The superficial, thinner portion

Stratum corneum;

Dead cells contain keratin,

embedded in a lipid matrix

Stratum lucidum; Dead cells filled

with eleidin (intermediate form of

keratin) surrounded by an oily

substance of lamellar body.

Stratum granulosum; cells

contain keratin & grains protein

called keratohyalin and give the

layer its grainy appearance. Cells

also secret lamellar body.

Stratum spinosum; cells joined by

desmosomes, keratin fibers give the

cells the spiny appearance

Stratum basal; cells divide by

mitosis to add new cells to the

superficial strataAnchor down upper tissue to lower tissue

intracellular fibrous

protein

- About 8% of the epidermal cells are melanocytes (melano

= black), which produce the pigment melanin.

- Melanin is a yellow- red or brown-black pigment that

contributes to skin color and absorbs damaging ultraviolet

(UV) light.

- Once inside keratinocytes, the melanin granules cluster to

form a protective veil over the nucleus, on the side toward

the skin surface to protect the nuclear DNA from damage

by UV light.

- Melanin granules effectively protect keratinocytes but

melanocytes are particularly at risk to damage by UV light.

Cells that present in the basale layer

Present only in skin of fingertips, palms, and soles

In the middle of the epidermis, consists of 3-5 layers

of flattened keratinocytes that are undergoing

apoptosis.

Distinctive feature of cells is the presence dark staining

granules of a protein called keratohyalin and

membrane-enclosed lamellar granules present in the

keratinocytes which fuse with the plasma membrane

and release a lipid-rich secretion.

Also, keratinocytes which produce the protein keratin and lamellar granules

(contain a waterproof sealant).

Dermis

Derived from mesoderm consist of:

Collagen fibers for toughness

Elastin fibers for elasticity

Blood capillaries for nourishment

Cells present include fibroblasts, macrophages, adipocytes

Hair (protection & reception)

Sweat gland (excretion, temperature regulation)

Sebaceous gland

Sense receptors for (sensory neurons) called the Meissner corpuscles

The dermis can be divided into:

Thin superficial papillary region

Thick deeper reticular region.

Papillary Layer

Reticular Layer

Compare the composition of the papillary and reticular

regions of the dermis.

Papillary

Superficial portion of dermis (about one-fifth);

consists of areolar connective tissue with thin collagen and fine elastic fibers;

contains dermal ridges (dermal papillae) that house blood capillaries, corpuscles of touch, and free nerve endings

Reticular

Deeper portion of dermis (about four-fifths)

consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers.

Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands.

Hypodermis

Also called subcutaneous

Bind the skin to the

underlying tissue

The primary tissue is

Adipose (fat cells), for:

Storing energy

Padding

Thermal Insulation

The secondary tissue is

loos connective tissue

Integumentary System

Epidermis

DermisHypodermis

Granulosum Lucidum

SpinosumBasal

Corneum

Summary

Review:

Q & A List the layers of skin.

List the layers of the epidermis.

What is melanin?

Describe the protection nature of melanin.

How is the epidermis different from the dermis in terms of

composition, blood supply, and function?

Which epidermal layer includes stem cells that continually

undergo cell division?

Skin Derivatives

Hairs, or pili, are present on most skin surfaces except the palms,

palmar surfaces of the fingers, the soles, and plantar surfaces of the feet.

In adults, hair usually is most heavily distributed across the scalp, in the

eyebrows, in the axillae (armpits), and around the external genitalia.

Anatomy of a Hair

Each hair is composed of columns of dead, keratinized epidermal cells.

The hair shaft is the superficial portion of the hair, which projects above the surface of the skin

The hair root is the portion of the hair that penetrates into the dermis, and sometimes into the subcutaneous layer.

The shaft and root of the hair both consist of three concentric layers of cells: medulla, cortex, and cuticle.

The cells of these layers contain large

amounts of pigment granules in dark

hair,

small amounts of pigment granules in grey

hair,

lack of pigment granules and the presence of

air bubbles in white hair

Front section of root hair

The shaft and root of the hair both consist

of three concentric layers of cells:

medulla,

cortex, and

cuticle

The cuticle of the hair, the outermost

layer, consists of a single layer of thin,

flat cells that are the most heavily

keratinized.

• The dense dermis

surrounding the hair

follicle is called the

dermal root sheath.

• Surrounding the root of

the hair is the hair

follicle, which is made up

of an external root

sheath and an internal

root sheath

• The external and internal

root sheath are referred

to as the epithelial

root sheath.

• The base of each hair follicle and its surrounding dermal root sheath

is an onion-shaped structure, the hair bulb contains the following;

• Papilla of the hair, which contains areolar connective tissue and many

blood vessels

• Hair matrix; Germinal layer of cells arise from the stratum basale,

the site of cell division. Hair matrix cells are responsible for the

growth of existing hairs and produce new hairs

Each nail consists of a nail body, a free edge, and a

nail root

The free edge is white because there are no

underlying capillaries.

The nail root is the portion of the nail that is buried

in a fold of skin.

The whitish, crescent-shaped area of the proximal

end of the nail body is called the lunula (little moon).

Anatomy of a nail

Anatomy of a nail

Skin Glands

References

For further reading please see:

Kenneth, S. S. (2017). Anatomy & physiology: The unity of form and

function. 8th edition. The McGraw−Hill Companies,. New york.

De Iuliis, G., & Pulerà, D. (2019). The dissection of vertebrates. 3rd

edition. Academic press. Elsevier, London.

Charles K. Weichert (2017). The Integumentary System. Elements of

chordate anatomy. 3rd edition. The McGraw−Hill Companies, New

york.

Murphrey, M. B., Miao, J. H., & Zito, P. M. (2018). Histology, stratum

corneum. In: StatPearls. StatPearls Publishing, Treasure Island (FL);

PMID.

Kardong, Kenneth V. (2019). Vertebrates : comparative

anatomy, function, evolution (8th edition). New York.