the integumentary system chapter 44. the integumentary system the outer covering of animal bodies is...
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The Integumentary System
Chapter 44
The Integumentary System The outer covering of animal
bodies is called the integument. In humans
The skin is the largest organ of the body
It accounts for 12-15% of body weight Occupies an average surface area of
about 1-2 meters
Integumentary Patterns of Animals Porifera (sponges)
Epidermis spicules
Cnidaria Epidermis
Integumentary Patterns of Animals Platyhelminthes
Cuticle Ectoderm
Nematoda Cuticle Ectoderm
Cross-section of Ascaris
Integumentary Patterns of Animals Annelida
cuticle setae
Arthropods exoskeleton made of
chitin undergoes ecdysis
(molting) – exoskeleton is shed periodically
Integumentary Patterns of Animals Mollusks
Shells of calcium
Echinoderms e.g., starfish spiny skin
Integumentary Patterns of Animals Vertebrates
pliable skin structures derived from the epidermal
cells Hair nails
Functions of The Integumentary System Protection from
Abrasion Bacteria, fungi, viruses UV radiation ( melanin pigment) dehydration
Support Temperature regulation
An important part of homeostasis
Functions of The Integumentary System Excretion
Another homeostasic function- maintaining water & salt balance
Secretion of the following: Oil Cerumin ( wax) Sebum ( from sebaceous glands) – softens &
lubricates skin and hair; slows water loss; antibacterial
Fatty acids - antibacterial
Functions of The Integumentary System Movement
In simple animals, contractions of the integument may be the only means of locomotion
In other animals, the integument is closely connected to the muscle layers.
In mammals, the integument is attached to the muscles by a connective tissue layer called the fascia
Functions of The Integumentary System Vitamin D production
Produced on the skin using the energy of UV light from sunlight
a serious deficiency of Vitamin D results in a crippling bone disease called rickets
Functions of The Integumentary System Reproductive
Mammary glands are actually derived from the ectodermal tissue of the integument.
Blood vessels in the skin serve as a blood reservoir for the body .
Functions of The Integumentary System Sensory reception
Sensory receptors in the skin detect external stimuli
Temperature Pressure and touch
Modifications of the Integumentary System Hair Fur Feathers Scales Quills Nails Claws Hooves
Beaks Horns Antlers Cerumin glands
wax Mammary glands
milk Sebaceous glands
Oil and sebum
Types of Tissues All four major types of tissues are
found in the Integumentary System Epithelial Connective Muscular Nervous
Structure of Human Skin
Structure of Human Skin Three Major
Layers A -- Epidermis B -- Dermis C -- Subdermis
(Subcutaneous Layer) – not strictly part of the skin
A
B
C
Epidermis Tissue - Stratified Squamous
Epithelium Epidermal cells called
keratinocytes produce keratin- a tough fibrous protein Keratin layers protect against water
loss & abrasion
Layers of the Epidermis Stratum corneum - outermost; cells are
flattened dead “bags” of keratin Stratum basale (Stratum germinativum)
The lowest or innermost layer generates new cells contains pigments: melanin(from
melanocytes) & carotene - skin color & UV protection
Layers of the Epidermis
Stratum corneum
Stratum basale or germinativum
Middle layers
S. Lucidum
S. Spinosum
S. granulosum
Dermis (“True Skin”) Lies below the
epidermis Cushions against
stretching & mechanical stress
Dense irregular connective tissue
sweat glands sebaceous glands hair follicles blood vessels nerve endings muscle
Glands in the Dermis All are exocrine glands
secrete to a duct or directly to surface Sweat Glands Sebaceous Glands
Sebum is a fatty mixture of oils and fatty acids; These glands are found on the hairy areas of skin
Sense Receptors Free Nerve endings – sense pain, heat
and cold Pacinian bulbs - pressure (found in
subdermis) Ruffini bulbs – deep pressure and
stretch Meissner’s bulbs, Merkel cells – light
touch Hair follicle receptors – light touch
Subdermis subcutaneous tissue ; lies beneath
the dermis technically not considered to be a
part of the skin anchors skin Mostly adipose tissue - stores fat
Insulation cushioning
Hair Composed of hard keratin Shaft – projects from the skin Root – part embedded in the skin Hair follicle – the epidermis folds down into
the dermis, producing a hair follicle. The deep end of the follicle is the hair bulb. The root grows out of the bulb
Hair tissue at the base of the hair bulb –
contains capillaries & free nerve endings which sense temperature & pain
receptors wrap around the bulb – act as very sensitive touch receptors
Sebaceous glands – secrete sebum to soften & waterproof the hair
Hair The arrector pili
muscle Contracts & raises the
hair You see “goose bumps”
under the skin Raising the hair
creates a trapped layer of still air that slows down heat loss & keeps the body warm
Nails A highly keratinized modification of the
epidermis Correspond to the hooves or claws of
other animals The nail matrix is where nail growth
occurs. The skin folds at the edge of the nail are
the cuticle.