Integumentary SystemsStructure & 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 Main organ in integumentary system is the skin, which , which makes it the largest organ in the body since it is 12-makes it the largest organ in the body since it is 12-15% of body weight!15% of body weight!– Made of two layers:Made of two layers:

Epidermis: outer layer of skin: outer layer of skin Dermis: inner layer of skin: inner layer of skin

Layers of SkinLayers of Skin

EpidermisEpidermis

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

EpidermisEpidermis

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)

DermisDermis

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 LayerSubcutaneous Layer Beneath dermis is subcutaneous layer

– Made of fat and connective tissue Help body absorb impacts, retain heat, store

food

Functions of SkinFunctions of Skin 1. Maintains homeostasis1. Maintains homeostasis

– Regulates internal body temperatureRegulates internal body temperature When temperature rises, small blood vessels in When temperature rises, small blood vessels in

dermis dilate (increase in circumference), dermis dilate (increase in circumference), allowing blood flow to increase, so blood loses allowing blood flow to increase, so blood loses heatheat

When temperature lowers, blood vessels When temperature lowers, blood vessels constrict (decrease in circumference), constrict (decrease in circumference), decreasing blood flow, so blood keeps in heatdecreasing blood flow, so blood keeps in heat

Feedback loop:Backward/forward

Feedback (Homeostasis) LoopInternal Body Temperature

ChangesBlood vessels

dilateBlood vessels

constrict

Blood flow increases

Blood flow decreases

Blood loses heat

Blood keeps in heat

Internal Body Temperature Normalizes

+ -

2. sensory organ2. sensory organ– Nerve cells get information from external Nerve cells get information from external

environment about pain, pressure, and environment about pain, pressure, and temperature and send message to braintemperature and send message to brain

3. produces Vitamin D3. produces Vitamin D– When exposed to UV light, skin makes Vitamin D, When exposed to UV light, skin makes Vitamin D,

which is essential to help body absorb calciumwhich is essential to help body absorb calcium Most calcium supplements contain Vitamin Most calcium supplements contain Vitamin

D for that same reasonD for that same reason 4. protective layer 4. protective layer

– Shields underlying tissues from physical and Shields underlying tissues from physical and chemical damage and from invading pathogens chemical damage and from invading pathogens (viruses and bacteria)(viruses and bacteria)

Skin injury and HealingSkin injury and Healing– Injuries to skin can occur due to scrapes, cuts, or burns, Injuries to skin can occur due to scrapes, cuts, or burns,

but how skin heals depends on severitybut how skin heals depends on severity Mild scrape (no blood, epidermis only)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)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 HealingSkin 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

Burn (Sun, chemicals, hot Burn (Sun, chemicals, hot objects)objects)– First degree (mild sunburn)First degree (mild sunburn)

Death of epidermal cellsDeath of epidermal cells Redness and mild painRedness and mild pain Heal in 1 week w/out scarHeal in 1 week w/out scar

– Second degreeSecond degree Damage of both epidermal Damage of both epidermal

and dermal cells and dermal cells Blistering and scaring may Blistering and scaring may

occuroccur

Skin Burns

Burn (sun, chemicals, hot Burn (sun, chemicals, hot objects)objects)– Third degreeThird degree

Destruction of both Destruction of both epidermal and dermal cellsepidermal and dermal cells

Skin function is lost, so skin Skin function is lost, so skin grafts are requiredgrafts are required

– Fourth degreeFourth degree Destruction through skin Destruction through skin

and into muscles, tendons, and into muscles, tendons, ligaments, and boneligaments, and bone

Skin Burns

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)

Bones: The Body’s Support

Axial vs. Appendicular Skeleton

– 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

Skeletal joints

Types of Joints Found in Human

Types of Joints Found in Human

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

Ligaments

Cartilage

Ends of bones are Ends of bones are covered in covered in cartilage– Allows for smooth Allows for smooth

movement between movement between bone endsbone ends

– Cushions jointsCushions joints

Bursae

Certain joints have fluid-filled 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

BONE

CARTILAGE

LIGAMENT

JOINT

MUSCLE

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 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

Human skeleton growth

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

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

Skeletal injury & disease

Bone Fracture TypesBone Fracture Types

Bone Fracture TypesBone 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

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 muscle3. Skeletal muscle: muscles attached to

bones

Muscle

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

Contraction (AKA peristalsis)

Item to be moved

Direction of movement

Smooth muscle of vessel or organ

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

– 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?

Skeletal Muscle

Opposing Muscle Pairs

Muscle Contracted

Muscle Relaxed

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

ActinMyosin

Relaxed Sarcomere

Z Disc

– 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

Yellow = actin (thin)

Pink = myosin (thick)

Black = Z disk

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

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

Muscle Strength and Exercise