THE INTEGUMENTARY SYSTEM
Presentation by
B.A. AMEYAW
THE INTEGUMENTARY SYSTEM
OBJECTIVES
• To describe the structure and functions of;
1. Skin
2. Appendages
• To identify the roles of the skin in maintenance
of body temperature
What is the Integumentary system?
• Name was derived from the
Latin word “integumentum,”
meaning “to cover”
• The skin is the largest organ
in the body
• It accounts for about 15% of
total body weight in adult
Without the integumentary system,
this is how the human body would
look like
• The Integumentary System consist of;
1. skin also known as integument or cutaneous membrane
Epidermis
Dermis
Hypodermis
2. Accessory structures
Hair
Nail
Exocrine glands
STRUCTURE OF THE SKIN
FUNCTIONS OF SKIN
• Provide protection of underlying tissues and organs: provides physical (eg
scratch without harming tissues underneath), and chemical protection (eg
wash clothes without the soap entering the body)
• Excretion of salts, water (through sweat), organic waste (sweating out after
taking alcohol)
• Regulate body temperature (provides insulation against heat loss via the
hypodermis since it contains fat tissues, and evaporation to cool down the
body)
• Production of melanin (melanin gives the skin its colour, provides
protection against ultraviolet radiation)
• Production of keratin (keratin is a protein that makes the skin strong,
protects the skin from abrasions, keratin is water resistant and hence
protects the skin from excessive water loss)
• Synthesis of vitamin D3 (vitamin D3 is good for calcium absorption)
• Detection of touch, pressure, vibration, temperature and pain
EPIDERMIS
• It is the outermost layer of the skin
• It is packed with cells called keratinocytes
• Keratinocytes are arranged in 4 or 5 layers depending on type of skin
• There are 2 different types of skin;
1. Thin skin
Thin skin is the skin that covers most part of the body
There are hair present on thin skin
The cells are arranged in 4 layers
The outermost layer (stratum corneum is thin hence thin skin)
EPIDERMIS
2. Thick skin
Skin on the palms of hand and soles of the feet
There are no hair present on thick skin
The epidermis of thick skin has 5 layers. The extra 1 layer in thick skin is
called stratum lucidum
• It is stratified squamous epithelium (stratified= many layers; squamous=
flat cells)
• The epidermis is avascular (lack blood vessels)
• Nutrients and oxygen get to these cells through diffusion from the
capillaries in the dermis
STRUCTURE OF EPIDERMIS
• Layers of the epidermis from bottom to top;
1. Stratum basale: This is the bottom or deepest layer of the
epidermis
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum (Absent in thin skin)
5. Stratum corneum: This is the top or superficial layer of
the epidermis
Stratum basale
• Also called stratum germinativum
• It is the deepest layer of the epidermis or the bottom of the epidermis
• It is attached to the basement membrane by hemidesmosomes
• It forms epidermal ridges that extends downward towards the dermis (this
develops our fingerprints)
• The dermis forms dermal papillae. The epidermal ridges and dermal papillae
interlink with each other to increase the surface area of the basement
membrane and strengthen the bond between dermis and epidermis
• The stratum basale has 3 types of cells;
1. Keratinocytes
2. Melanocytes: produce melanin
3. Tactile (Merkel) cells: respond to touch. They are found in hairless skin such as palms of
hand and soles of feet. These cells make those skin extra sensitive to touch
Stratum spinosum
• Consists of several layers of keratinocytes bound by desmosomes
• Produced by division of stem cells in the stratum basale
• The division of cells continue in this stratum, thereby increasing the
thickness of the epithelium
• As they are pushed farther upward, they cease dividing. Instead, they
produce more keratin filaments, which cause the cells to flatten
• Contain dendritic (Langerhans) cells which phagocytize (engulf)
pathogens that pass the superficial layers “presenting” it to the
immune system for a response.
Stratum Granulosum
• It has 2 to 5 layers of keratinocytes derived from stratum spinosum
• Division of cells stop and they start producing large quantities of
keratin and keratohyalin
• Keratin
They are tough fibrous proteins that makes up hair nails and make
the skin strong
They make the skin water resistant and resistant to abrasion
• Keratohyalin
They are dense granules that promotes dehydration of cells
Promotes aggregation and cross-linking of keratin fibers in
neighbouring cells
Stratum Lucidum
• Found only in thick skin
• Made up of flat densely packed cells filled with keratin
• This layer decreases the amount of friction/wear/tear
on the cells and tissues below
Stratum Corneum
• It is the outermost/superficial layer of the skin
• In thin skin, there are about 30layers of keratinized cells
• Thick skin has over 100layers of keratinized cells
• Cells are tightly packed together
• Cells are water resistant
• Cells are connected by desmosomes
• Cells are shed and replaced frequently
DERMIS
• The dermis is beneath the epidermis
and is composed of connective tissue
• Contains the accessory structures
• Hair follicles
• Sweat glands
• Oil glands
• Contains blood vessels, which supply
nutrients and oxygen to the cells
• Contains sensory receptors (nerves) for:
• Touch
• Heat or cold
• pain
• pressure
DERMIS
• The dermis is divided into two layers;
1. Papillary layer:
This is the outer layer
Consist of connective tissues
Has smaller capillaries, lymphatics vessels and sensory neurons that supply parts of
the epidermis with nutrients
 It is arranged into microscopic structures (dermal papillae) that form ridges. These
are responsible for finger- and footprints
2. Reticular layer:
It is the deep layer of the dermis
Consist of connective tissues
Has larger blood vessels, lymphatics vessels and nerve fibers
Contains collagen (protein that hold skin together) and elastic fibers to provide
strength and flexibility respectively
Innervation of the skin
• The dermis contains nerve fibers
• The nerve fibers control blood flow and gland secretions
• Some sensory receptors in the dermis;
Tactile corpuscles (Meissner’s corpuscles): They are located in the
dermal papillae or top of the dermis. They send information to the
brain when the skin experiences a light touch.
Lamellated corpuscles (Pacinian corpuscles): They are located in the
reticular layer of the dermis or deep layer of the dermis. They send
signals to the brain when the skin experiences a deep pressure or
vabration
HYPODERMIS
• It is also called the subcutaneous layer
• Lies below the integument
• Made of connective tissue and adipose tissues
• The functions of the adipose tissues are;
Provide insulation (keeps the body warm)
Stores energy (fatty acid in the form of triglycerides)
Act as shock absorber
• It is connected to the reticular layer of dermis by connective tissue
fibers such as collagen
• It allows for separate movement of skin without damages to the
muscles and tissues
SKIN COLOUR
• Three pigments are most responsible for normal skin colors
1. Haemoglobin
2. Carotene
3. Melanin
Synthesis of Vitamin D3
• In the presence of UV radiation, the epidermal cells produce
cholecalciferol (Vitamin D3).
• The Vitamin D3 produced in skin enters the blood stream and gets to
the liver and kidneys where it is converted into a hormone called
calcitriol.
• Calcitriol is a hormone that helps in the absorption of calcium and
phosphorus from the gastro-intestinal tract.
• Insufficient Vitamin D3 causes rickets
ACCESSORY STRUCTURES
• Hair
• Nail
• Exocrine glands
• They are derived from epidermal tissues
• They are located in the dermis
• Some project through the surface of the skin
Hair
• With exception of soles, palms, lips, and portions of external genitalia,
the human body is covered with hair
• A hair is also known as a pilus
• It is a slender filament of keratinized cells that grows from an oblique
tube in the skin called a follicle
Structure of the Hair and Follicle
• A hair is divisible into three zones
along its length;
1. Bulb: a swelling at the base where
the hair originates in the dermis
2. Root: it is the remainder of the
hair within the follicle
3. Shaft: It is the portion above the
skin surface.
• Except near the bulb, all the tissue
is dead. A bit of vascular
connective tissue called the
papilla grows into the bulb and
provides the hair with its sole
source of nutrition
Cross sectional view of hair
• In cross section, a hair reveals three
layers:
1. Medulla: a core of loosely arranged
cells and air spaces
2. Cortex: composed of densely
packed keratinized cells
3. Cuticle: a single layer of scaly cells
that overlap each other. They interlock
with the scales of the hair cuticle and
resist pulling on the
hair.
Types of hair
• Over the course of lives, three kinds of hair growth develop;
1. Lanugo: fine, downy, unpigmented hair that appears on the fetus in the
last 3 months of development
2. Vellus: fine, unpigmented hair. Replaces most lanugo hair by time of
birth
3. Terminal: longer, coarser, and pigmented. It occurs on the scalp,
eyebrows, and eyelashes. At puberty, it replaces the vellus in the axillary,
pubic regions, on the face of males (to form the beard), and to varying
degrees on the trunk and limbs
How hair grows (cycles)
1.
2.
3.
4.
5.
Hair is produced in the hair bulb
Blood vessels in the papilla supply the hair bulb with nourishment
Division of cells in the hair follicle gives rise to new hair
These cells divide and undergo keratinization
Hair grows longer as cells are added to the base of the hair root
Accessory structures of hair
1. Arrector pili muscles (piloerector muscles):
• bundle of smooth muscles cells extending
from dermal collagen fibers to a bulge in the
root sheath slightly above the middle of the
follicle
• In response to cold, fear, or other stimuli, the
sympathetic nervous system stimulates the
piloerector muscle (to contract) and makes
the hair stand up
• In humans, it pulls the follicles into a vertical
position and causes “goose bumps”
2. Sebaceous glands:
• secrete sebum (oily secretion) to lubricate
the hair, and control bacteria
Functions of hair
• Provides protection from UV radiation
• Insulates the body as heat loss
• Guards openings of the body against insects and particles
• Sensitive to very light touch
Nail
• Develops from the epidermis (specifically stratum corneum )
• Formed in the nail bed or matrix
• Epidermal cells are densely packed together and filled with parallel
fibers of hard keratin
• Appear pink because their translucency reveals the vascular tissue
beneath.
• They aid in grasping, scratching, and protecting fingers and toes
Parts of nail
• The lunula is the white halfmoon at the nail base
• The nail bed is a thick layer of
epithelial skin where the nail
rests on
• The hyponychium is the
epithelium of the nail bed
• Eponychium (thin layer of
epithelium) covers the proximal
end of nail during development;
in the adult, it remains at the
nail base only and is called the
cuticle.
Sweat glands (Sudoriferous glands)
• Distributed over the entire skin surface
• Approximately 3 million sweat glands throughout the body
• Most are found under the arms, palms of hands, soles of feet and
forehead
• They are tubular with a coiled base in the dermis and a tube-like duct
which extends to form a pore in the epidermis
• Water filters through the thin walls from surrounding tissue
• Water is mixed with small amounts of waste material such as ammonia and
uric acid
• Glands may be activated by heat, pain, fever and nervousness
Types of sweat glands
• Two types of sweat glands;
1. Eccrine (merocrine):
Produces perspiration and functions throughout
life
Assists in body heat regulation (cool the body)
Perspiration is 99% water
Average fluid loss is about 150ml per day
though sweating is highly variable, depending
on physical activity and environmental
temperature
2. Apocrine:
larger than eccrine glands
Found in axilla and genitalia
Enlarges and begins to function during puberty
Their ducts lead into nearby hair follicles rather
than opening directly onto the skin surface
Secretes a sticky, cloudy secretion that break
down and causes odor
Sebaceous glands (oil glands)
• Produce a mixture of lipids and proteins
called sebum
• Function to prevent drying of skin and
hair
• Are located primarily on the scalp, face
and upper portion of the body
• Increase in size and produce a greater
amount of sebum in coordination with
increased hormone levels
• Make skin waterproof
• Inhibit bacteria growth
• Plugged sebaceous glands (oil glands)
will produce blackheads or pimples
• Acne Vulgaris is an inflammation of
sebaceous glands
Thermoregulation
• When the body is too hot
and needs to release heat:
• When the body is cold and
needs to conserve heat:
• A signal from the hypothalamus
(part of the brain) is sent to the
skin and warm blood is brought
closer to the surface of the skin
• Sweat glands begin producing lots
of sweat. When sweat evaporates,
it carries heat away from the body,
cooling the body
• The brain senses cold body
temperatures
• The hypothalamus sends signals
that constrict the Blood vessels,
reducing blood flow near the body
surface and retaining heat deeper
in the body
• Piloerector muscles causes
the formation of “goose
bumps”
End of presentation
Thank you