Download Unit 18

Integumentary Systems
Structure & Functions of Integumentary System
– Integumentary system consists of layers of the four
types of body tissues:
 1) epithelial tissue - outer layer of skin
 2) connective tissue - tough & flexible protein
fibers that act to hold body together
 3) muscle tissue - interact w/ hairs on skin &
respond to stimuli like cold and fright
 4) nervous tissue - detects external stimuli like
pain and pressure (Chapter 19)
Skin: The Body’s Protection

Main organ in integumentary system is the skin, which
makes it the largest organ in the body since it is 1215% of body weight!
– Made of two layers:
 Epidermis: outer layer of skin
 Dermis: inner layer of skin
Layers of Skin
Epidermis
Outermost layer of skin made of 2 parts:
exterior and interior portions
 Exterior: 25-30 layers of dead, flattened cells that
are continually being shed
– Even though dead, are important since contain
keratin which helps protect living cells
underneath
Epidermis

Interior: living cells that continually divide to replace
dead cells
– Contain pigment melanin that colors skin and
protects it from damage by solar radiation
 Melanin is not sole protector for sun damage –
can get skin cancer if are dark pigmented!
– process of shedding takes 28 days (4 weeks)
Dermis
Inner, thicker portion of skin
 Contains many structures:
– Blood vessels (arteries & veins)
– Nerves & nerve endings
– Hair follicles
– Sweat glands
– Sebaceous (oil) glands

– Muscles (to make hair stand up)
Subcutaneous Layer

Beneath dermis is subcutaneous layer
– Made of fat and connective tissue
 Help body absorb impacts, retain heat, store
food
Functions of Skin

1. Maintains homeostasis
– Regulates internal body temperature
 When temperature rises, small blood vessels in
dermis dilate (increase in circumference),
allowing blood flow to increase, so blood loses
heat
 When temperature lowers, blood vessels
constrict (decrease in circumference),
decreasing blood flow, so blood keeps in heat
Feedback loop:
Backward/forward
Feedback (Homeostasis) Loop
+
Internal Body
Temperature
Changes
-
Blood vessels
dilate
Blood vessels
constrict
Blood flow
increases
Blood flow
decreases
Blood loses
heat
Blood keeps in
heat
Internal Body
Temperature
Normalizes
 2. sensory organ
– Nerve cells get information from external
environment about pain, pressure, and
temperature and send message to brain
 3. produces Vitamin D
– When exposed to UV light, skin makes Vitamin D,
which is essential to help body absorb calcium
 Most calcium supplements contain Vitamin
D for that same reason
4. protective layer
– Shields underlying tissues from physical and
chemical damage and from invading pathogens
(viruses and bacteria)
Skin injury and Healing
– Injuries to skin can occur due to scrapes, cuts, or burns,
but how skin heals depends on severity
 Mild scrape (no blood, epidermis only)
 Deepest layer of affected epidermal cells start to
divide to fill in gap left by abrasion
 Cut (blood, epidermis and dermis)
 Blood flows out of wound until clot forms
 Scab develops, creating barrier between bacteria
on skin and underlying tissues
Skin injury and Healing
 Bacteria already present in wound gets killed by
white blood cells that migrate to site
 New skin cells begin repairing wound from
beneath
 Scab ‘falls’ off when new skin is formed
 Large wound needs high amount of connective
tissue which may form a scar
Healing of a Cut
Before
Cut in skin
Blood pools, creating scab
Skin cells regenerate from
bottom up
Skin Burns

Burn (Sun, chemicals, hot
objects)
– First degree (mild sunburn)
 Death of epidermal cells
 Redness and mild pain
 Heal in 1 week w/out scar
– Second degree
 Damage of both epidermal
and dermal cells
 Blistering and scaring may
occur
Skin Burns

Burn (sun, chemicals, hot
objects)
– Third degree
 Destruction of both
epidermal and dermal cells
 Skin function is lost, so
skin grafts are required
– Fourth degree
 Destruction through skin
and into muscles, tendons,
ligaments, and bone
Bones: The Body’s Support
Skeletal System Structure
 Adult human skeleton contains 206 bones! Made
of two main parts:
– Axial skeleton: skull and bones that support it
like vertebral column, ribs, sternum
– Appendicular skeleton: bones of arms and legs
(appendages), and all structures associated with
them (shoulder, hips, wrists, ankles, fingers,
toes)
Axial vs. Appendicular Skeleton
Skeletal joints
– Bones meet other bones at areas called joints
 Joints facilitate movement of bones in
relation to one another
– Joints can be fixed (non-moveable) or
non-fixed (moveable)
 Fixed joints: skull
Skeletal joints
 Non-fixed joints: knee, wrist, etc.
- 4 types of moveable joints:
* Ball-and-socket: hips, shoulders
* Pivot: twisting arm at elbow
* Hinge: elbows, knees, fingers, toes
* Gliding: wrists, ankles
Types of Joints Found in Human
Types of Joints Found in Human
Ligaments

Joints are held together by
ligaments
– Ligament: tough band of
connective tissue that
attaches one bone to
another
 Joints with a large
range of motion
(knee) have many
ligaments
Cartilage

Ends of bones are
covered in cartilage
– Allows for smooth
movement between
bone ends
– Cushions joints
Bursae

Certain joints have fluidfilled sacs called bursae
(bursa is singular)
– Outside of joint
between tendon and
bone to reduce friction
Tendons

Muscles are attached to
bones with tendons
– Tendons are thick
bands of connective
tissue
JOINTS
MUSCLE
BONE
JOINT
CARTILAGE
LIGAMENT
TENDON
Types of Bone

Two types of bone tissue:
– Compact bone and spongy bone
 Compact bone: hardened bone that contains
tubular structures called osteons (or Haversian
systems)
– Surrounds spongy bone to protect it
 Spongy (cancellous) bone: less dense bone with
many holes and spaces
– Living bone cells are called osteocytes, which
receive oxygen and nutrients from small blood
vessels
Types of Bone
Formation of Bone

Skeleton of human embryo is actually made of
cartilage, not bone (same as what nose is made of)
– Not until embryo is 9 weeks does cartilage get
replaced by bone
 When blood vessels penetrate cartilage
membrane, stimulate it to become osteoblasts
(precursors to osteocytes)
Bone
Human skeleton growth
Human skeleton is almost 100% bone, with cartilage
found only in places where flexibility is needed –
nose, ears, vertebral disks, and joint linings
 Bone grows in length and diameter as result of sex
hormones released during growth
– Length: from cartilage plates at ends of bones
– Diameter: from outer surface of bone
 After growth stops, bone-forming cells are involved in
repair and maintenance

Skeletal System Functions

Function of skeleton is five-fold:
– 1. Provide framework for tissues of body
 Allows muscles to attach to bones so they can
provide movement to body
– 2. Protects internal organs
– 3. Produce blood cells
 Red marrow: where red blood cells, white blood
cells, blood clotting factors are produced
– found in humerus, femur, sternum, ribs,
vertebrae, pelvis
Skeletal System Functions

Function of skeleton is five-fold:
– 4. Store fat
 Yellow marrow: many other bones store fat in
here
– 5. Mineral storage
 Body’s supply of calcium and phosphorous is
stored in bone
Skeletal injury & disease

Skeleton is vulnerable to injury and disease
– Broken bones
 Too much force against bone can cause it to
break or fracture
– Physician must set bone back in place so
new osteocytes may form in broken area
and put two ends back together
Skeletal injury & disease

Skeleton is vulnerable to injury and disease
– Osteoporosis
 Loss of bone volume and mineral content
which leads to bones becoming more porous
and brittle and more susceptible for breakage
– More common in older women since they
produce lower amounts or estrogen which
aids in bone formation
Bone Fracture Types
Bone Fracture Types
Osteoarthritis

Joints can become
diseased
– Arthritis:
inflammation of the
joints
 Bone spurs are
outgrowths of
bone inside the
joints so it limits
mobility
Muscle
Muscles
– Nearly half of body mass is muscle!
 Muscle: groups of fibers, or cells, bound
together. Almost all muscle fibers have been
present since birth
– 3 main types of muscle:
1. Smooth muscle: walls of internal organs
and blood vessels
2. Cardiac muscle: heart muscle
3. Skeletal muscle: muscles attached to
bones
Muscle Types
Muscle Types
Smooth Muscle
– Made up of sheets of cells that form a lining for
organs
– Most common function is to squeeze via
contractions, exerting pressure on space inside
tube or organ to move material inside it
 Ex: food bolus gets squeezed through digestive
system until it comes out; semen gets
squeezed through vas deferens, then urethra
Movement of Smooth Muscle
Smooth muscle of vessel or organ
Contraction (AKA peristalsis)
Item to be moved
Direction of
movement
Contractions are involuntary (can’t
be controlled by human) so
smooth muscle is considered to be
an involuntary muscle
Cardiac Muscle
– Found in heart and is adapted to generate
and conduct electrical impulses!
– Considered an involuntary muscle
Skeletal Muscle
– Muscle that is attached to and moves bones
– Makes up majority of muscles in body which work
in opposing pairs
 Muscle X on one side of bone, Muscle Y on
other side of bone
– If Muscle X is contracted, Muscle Y is
relaxed, and vice versa
– Considered a voluntary muscle since contractions
can be controlled
 How do we contract our muscles?
Opposing Muscle Pairs
Muscle
Relaxed
Muscle
Contracted
Muscle Names
Skeletal Muscle Contraction

All muscle tissue is made of muscle fibers, which are
very long, fused muscle cells
– Each fiber is made of smaller units called myofibrils
 Myofibrils made of thick and thin filaments
– Thick filaments: myosin
– Thin filaments: actin
 Myofibril can be divided into segments called
sarcomeres
Muscle Contraction
Relaxed Sarcomere
Z Disc
Myosin
Actin
– How do muscles contract? How do they know that
you want to “make a muscle?”
 Sliding Filament Theory
Sliding Filament Theory

Sliding filament theory: when signaled, actin filaments
within each sarcomeres slide toward one another,
shortening sarcomeres in a fiber and causing muscle
to contract
– Myosin fibers do NOT move
– When skeletal muscle receives a signal (via brain),
calcium is released inside muscle fibers, causing
two sides of sarcomere to “slide” toward each
other = contraction
– When signal is gone, calcium gets absorbed,
sarcomeres relax and slide away back into place
Sliding Filament Theory
Contracted Sarcomere
Black = Z disk
Yellow = actin
(thin)
Pink = myosin
(thick)
Muscle Strength and Exercise

Muscle strength does not depend on amount of
fibers but does depend on thickness of fibers
– You are born with the number of fibers you will
always have, but exercise can increase thickness
of each fiber making entire muscle bigger
 Exercise stresses muscle fibers slightly, so to
compensate for workload, fibers increase in
diameter by adding myofibrils
Muscle Strength and Exercise

Energy that muscles need to
contract comes from ATP
produced by cellular respiration
(aerobic and anaerobic
processes)
– Most energy comes from
aerobic respiration when
oxygen (from breathing) is
delivered to muscle cells
during rest or MODERATE
activity
Muscle Strength and Exercise
– During VIGOROUS activity (when we have tendency
to hold our breaths & delivery of oxygen is not as
fast as it needs to be), anaerobic respiration kicks in
and in addition to ATP being made, lactic acid
fermentation makes lactic acid which makes
muscles cramp up
 Lactic acid build up gets sent into bloodstream,
where triggers rapid breathing (panting!)
 Inhalation of oxygen again breaks down lactic
acid & cramps go away