Anatomy & Physiology: Body Organization

• Anatomy studies the structure of body parts.
• Physiology studies how body parts function.
• Histology studies tissues under a microscope.
• Standard anatomical position involves standing upright, facing forward, with arms at the sides, palms forward, and feet flat on the ground.
• Anatomical position serves as a reference for anatomical terms.

Levels of Human Organization

• The chemical level is composed of atoms and molecules.
• The cellular level represents the basic structural and functional unit of life.
• The tissue level comprises groups of similar cells performing specific functions.
• The organ level consists of two or more tissues working together.
• The organ system level involves multiple organs working together.
• The organism level represents the entire human body.

Human Body Systems & Example Organs

• The integumentary system includes skin, hair, and nails.
• The skeletal system includes bones, cartilage, and ligaments.
• The muscular system consists of skeletal muscles.
• The nervous system comprises the brain, spinal cord, and nerves.
• The endocrine system includes glands such as the thyroid and adrenal glands.
• The cardiovascular system includes the heart and blood vessels.
• The lymphatic/immune system includes lymph nodes and the spleen.
• The respiratory system includes the lungs and trachea.
• The digestive system includes the stomach, intestines, and liver.
• The urinary system includes the kidneys and bladder.
• The reproductive system includes the ovaries and testes.
• The dorsal cavity contains the cranial cavity (brain) and the vertebral cavity (spinal cord).
• The ventral cavity contains the thoracic cavity (heart, lungs) and the abdominopelvic cavity (digestive, urinary, reproductive organs).

Body Planes

• The sagittal plane divides the body into left and right halves.
• The frontal (coronal) plane divides the body into front (anterior) and back (posterior) halves.
• The transverse plane divides the body into top (superior) and bottom (inferior) halves.

Positional Terms

• Supine refers to lying face up.
• Prone refers to lying face down.

Four Basic Tissue Types

• Epithelial tissue covers body surfaces and lines cavities.
• Connective tissue supports and connects body parts.
• Muscle tissue is responsible for movement.
• Nervous tissue conducts electrical impulses.

Epithelial Tissue

• Simple epithelium is a single layer of cells that facilitates absorption and filtration.
• Stratified epithelium consists of multiple layers and provides protection.

Types of Epithelial Tissue

• Simple squamous epithelium has flat cells and is found in the alveoli of the lungs and blood vessels.
• Mesothelium is a specialized simple squamous epithelium that lines body cavities.
• Simple cuboidal epithelium consists of cube-shaped cells and is found in kidney tubules.
• Simple columnar epithelium consists of tall cells and is found in the digestive tract, potentially including goblet cells.
• Stratified squamous epithelium has multiple layers and is found in the skin and esophagus.
• Keratinized stratified squamous epithelium contains keratin for waterproofing and is found in the skin.

Connective Tissue

• Basic features of connective tissue: matrix (fibers + ground substance), fibroblasts, and immune cells.

Types of Connective Tissue

• Areolar connective tissue cushions organs and is located under the skin.
• Reticular connective tissue supports lymphoid organs such as the spleen and lymph nodes.
• Dense connective tissue is categorized into regular (parallel fibers in tendons and ligaments) and irregular (random fibers in the dermis of the skin).
• Tendons connect muscle to bone.
• Ligaments connect bone to bone.

Functions of Skin

• Protection
• Body temperature regulation
• Sensory reception
• Vitamin D synthesis
• Excretion

Layers of the Skin

• The epidermis is the outer, avascular layer that contains keratin; it is categorized into thick skin (palms, soles) with five layers and thin skin (most of body) with four layers.
• The dermis is a connective tissue layer that contains blood vessels and nerves.
• The subcutaneous layer (hypodermis) stores fat and insulates.
• Melanin is a skin pigment produced by melanocytes and protects against UV radiation.

Basic Structure of Long Bone

• The diaphysis is the shaft of the bone.
• The epiphysis are the ends of the bone.
• The medullary cavity is the hollow center filled with bone marrow.

Bone Classification by Shape

• Long bones: femur, humerus
• Short bones: carpals, tarsals
• Flat bones: skull, ribs
• Irregular bones: vertebrae, pelvis

Bone Components

• Compact bone is dense and is found in the outer layer.
• Spongy bone is porous and contains red bone marrow.

Bone Cells

• Osteocytes maintain bone.
• Osteoblasts build bone.
• Osteoclasts break down bone.

Joint Classification

• Fibrous joints provide no movement.
• Cartilaginous joints allow slight movement.
• Synovial joints allow free movement.
• Flexion decreases the angle (bending elbow).
• Extension increases the angle (straightening elbow).
• Abduction moves away from the midline.
• Adduction moves toward the midline.
• Inversion turns the foot inward.
• Eversion turns the foot outward.
• Supination turns the palm up.
• Pronation turns the palm down.
• Opposition moves the thumb to the fingertips.
• Protraction moves forward (jaw).
• Retraction moves backward (jaw).
• Elevation lifts up (shoulders shrug).
• Depression moves down.

Muscle Properties

• Extensibility allows muscles to be stretched.
• Elasticity allows muscles to return to their original shape.

Muscle Tissue Types

• Skeletal muscle is voluntary, striated, and attached to bones.
• Cardiac muscle is involuntary, striated, and found in the heart.
• Smooth muscle is involuntary, non-striated, and found in the walls of organs.

Skeletal Muscle Structure

• Epimysium surrounds the entire muscle.
• Endomysium surrounds individual muscle fibers.
• Fascicles are bundles of muscle fibers.

Sarcomere Structure

• Thin filaments are composed of actin.
• Thick filaments are composed of myosin.
• The Z-line marks the end of a sarcomere.
• The A band is the dark band (thick + thin filaments).
• The I band is the light band (only thin filaments).
• The H band is the center of the sarcomere (only thick filaments).

Learn about anatomy, which studies the structure of body parts, and physiology, which studies their functions. Explore the levels of human organization, from chemical to organism, and major body systems. Each level and system has specific functions that contribute to the overall function of the human body.