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 12-15% 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 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 MUSCLE BONE TENDON JOINT CARTILAGE LIGAMENT

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: Smooth muscle: walls of internal organs and blood vessels Cardiac muscle: heart muscle 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 Contractions are involuntary (can’t be controlled by human) so smooth muscle is considered to be an involuntary muscle Direction of movement

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 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 Relaxed Sarcomere Z Disc Actin Myosin 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