Ch 37 – Introduction to Body Structure

Outline 1. Body organization 2. Skeletal system 3. Muscular system 4. Skin, hair and nails

37.1 Levels of structural organization Cells are grouped into 4 types of body tissues: EPITHELIAL TISSUE - Cover or line body surfaces; some are capable of producing secretions with specific functions. Ex. outer layer of skin CONNECTIVE TISSUE - Connects and supports parts of the body; some transport or store materials. Ex. Blood, Bone, and Adipose Tissue (Fat) MUSCLE TISSUE - Specialized for CONTRACTION, which brings about movement. Ex. Skeleton Muscles &Heart NERVE TISSUE - Specialized to generate and transmit electrochemical Impulses that regulate body functions. Ex. Brain and Optic Nerves

Body Tissues

Stem cells Stem Cells- Any embryonic stem cell is capable of becoming any type of tissue found in the adult body Read section in book.

Cell Differentiation Video

Stem cell research

Know general system function – p. 848 in Book!

Body cavities House and protect the major internal organs. Organs are suspended in a fluid that supports their weight and prevents them from being deformed by body movements.

CRANIAL CAVITY - encases the brain. SPINAL CAVITY - extending from the cranial cavity to the base of the spine, surrounds the Spinal Cord. THORACIC CAVITY - The upper compartment, contains the heart, the esophagus, and the organs of the respiratory system - the lungs, trachea, and bronchi. ABDOMINAL CAVITY - The lower compartment, contains organs of the digestive, reproductive, and excretory systems. Separated by diaphragm

Endothermy Like all mammals, humans are endotherms. Humans maintain a fairly constant body temperature of 98.6ºF. Very high temperatures, such as those during a fever, can be dangerous b/c they can inactivate critical enzymes. To release heat, blood flow is increased to blood vessels just under the skin. To retain heat, blood is shunted away from the skin.

37.2 Muscle and Bones

37.2 Skeletal system Your skeleton is made mostly of bone – a type of hard connective tissue, that is constantly being formed and replaced. 206 bones Axial skeleton – skull, spine, ribs and sternum (forms axis) Appendicular –forms appendages or limbs; arms, legs, pelvis, shoulder (comes off of axial)

Axial & Appendicular

Do NOT need to know all bones for the scope of this class

Bone

Bone layers Periosteum – tough exterior membrane – contains many blood vessels that supply nutrients to the bone Compact bone – outer layer of bone – compact Spongy bone – loosely structured network of connective tissue

Bone Marrow Bone marrow – soft tissue Red bone marrow – begins production of all blood cells and platelets Yellow bone marrow – mostly fat, stores energy

Bone growth In early development the skeleton is mostly cartilage, a type of connective tissue that serves as a template for bone formation. During development, most cartilage is gradually replaced by bone as minerals are deposited. Deposits of calcium and other minerals harden bones, enabling them to withstand stress.

Bone growth In compact bone, new cells are added in layers around narrow, hollow channels called Haversian canals. Osteocytes – bone cells become embedded in the tissue Build bone Bones continue to thicken and elongate through adolescence as bone cells replace cartilage. Cartilage degenerates as new bone cells are added, causing bones to lengthen. Look for open bone plates

Bone growth

Osteoporosis Bone loss – porous bone – brittle bones Bones respond to stress = exercise B/c women’s bones are smaller, cannot afford to lose as much tissue as men. Decrease in sex hormones after menopause has also been linked to decrease in bone production

Dowager’s hump - lose out of vertebrae Prevention- exercise, nutrition, calcium supplements Weight-bearing and resistance exercise Nutrition – calcium, leafy green veggies, whole grains, legumes

Body joints JOINT – where two bones meet Bones held together by ligaments (bone to bone) Stretch only so far Stabilize Prevent range of motion Ligament injury - SPRAIN Different types of joints for different fcn Immovable – little or no movement – skull Slightly movable – limited – vertebrae Freely movable –shoulder, hip etc

Table 2 - Movable joints know – p. 854 book! JointType of movement Examples Ball and socketAll types Shoulders and hips Pivot JointRotation Top of spine (turning of head) Hinge JointBending & straightening Elbows, knuckles of fingers & toes Gliding jointSliding motion Wrists and ankles Saddle joint Rotation, bending, & straightening Base of thumbs

37. 3 Muscle Tissue 3 types: in book p Skeletal muscle – voluntary muscle b/c you can consciously control its contractions. Moves bones in the trunk and limbs. 2. Smooth muscle – involuntary b/c you cannot consciously control its slow, long lasting contractions. 3. Cardiac muscle – involuntary and found in the heart

Muscles are attached to bones by tendons. Muscle pairs move parts of the body by pulling on bones Flexor – causes joint to bend Extensor – causes joint to straighten

Tendon injury Strain (tendons strain; ligament sprain) Tendonitis – inflammation of a tendon

Muscle structure Sarcomeres shorten during muscular contraction During muscle contraction, actin & myosin interact. A and M are protein filaments Energy is needed for muscles to contract.

Before a muscle is stimulated is relaxed Stimulated by a signal molecule form a nerve cell – cause actin & myosin to slide and overlap Sarcomere is contracted when myosin and actin completely overlap each other.

Rigor mortis – after death, ATP production stops. Without ATP, myosin heads attach to actin filaments, but cannot detach. As a result, muscles are locked into position, making the body rigid. This condition lasts up to 25 hours after death.

37.4 Skin, hair, nails Skin makes up about 15% of your body weight – is the largest organ of the body! Skin, hair, nails make up the integumentary system

Layers of the skin

SKIN EPIDERMIS - Outermost layer – about as thick as the page of your book – made of several layers of epithelial cells DERMIS – innermost layer contains BLOOD VESSELS, NERVE ENDINGS, GLANDS (OIL & SWEAT), SENSE ORGANS, SMOOTH MUSCLES, AND HAIR FOLLICLES. SUBCUTANEOUS TISSUE - Layer of connective tissue which is mostly fat Anchors skin to underlying organs Acts a shock absorber, provides additional insulation to help conserve body heat, and stores energy.

Skin Cancer Can result from genetic mutations caused by overexposure to UV radiation. Most common type of skin cancer are carcinomas which originate in skin cells that do not produce pigments. Malignant melanomas grow quickly and spread to other parts of the body. Basal cell carcinoma

ABCD’s of Recognizing Melanomas