Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms must maintain homeostasis to survive.
• All living organisms share several key characteristics, including organization, metabolism, reproduction, growth, and response to stimuli.

Subdisciplines of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell biology studies the structure, function, and behavior of cells.
• Ecology studies the interactions of organisms with each other and with their environment.
• Evolutionary biology studies the origin and descent of species, as well as their changes over time.
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular biology studies the molecular basis of biological activity.
• Physiology studies the functions and mechanisms of living organisms and their parts.
• Zoology studies animals, including their physiology, anatomy, behavior, genetics, ecology, evolution, and classification.

Human Anatomy

• Human anatomy studies the structure of the human body.
• It includes the study of individual organs and systems.
• Anatomy is closely related to physiology, which studies the function of the body's structures.

Levels of Organization

• The human body is organized in a hierarchical manner.
• Chemical level: atoms and molecules
• Cellular level: cells are the basic units of life
• Tissue level: tissues are groups of similar cells performing a specific function
• Organ level: organs are composed of two or more different tissues
• System level: organ systems consist of different organs that work together closely
• Organismal level: the human organism is the sum total of all structural levels working together to keep us alive

Organ Systems

• Integumentary system: skin, hair, and nails; protects the body and regulates temperature
• Skeletal system: bones, cartilage, and joints; provides support and facilitates movement
• Muscular system: skeletal muscles; enables movement, maintains posture, and produces heat
• Nervous system: brain, spinal cord, and nerves; controls and coordinates bodily functions
• Endocrine system: glands that secrete hormones; regulates growth, reproduction, and metabolism
• Cardiovascular system: heart and blood vessels; transports blood, oxygen, and nutrients
• Lymphatic system: lymphatic vessels and lymphoid tissues; defends against infection and disease
• Respiratory system: lungs and airways; exchanges gases between the body and the environment
• Digestive system: mouth, esophagus, stomach, intestines, liver, and pancreas; breaks down food and absorbs nutrients
• Urinary system: kidneys, ureters, bladder, and urethra; eliminates waste and regulates water balance
• Reproductive system: gonads and associated organs; enables reproduction

Anatomical Terminology

• Anatomical position: standard reference point, body erect, feet slightly apart, palms facing forward.
• Superior (cranial): toward the head end or upper part of a structure or the body; above.
• Inferior (caudal): away from the head end or toward the lower part of a structure or the body; below.
• Anterior (ventral): toward or at the front of the body; in front of.
• Posterior (dorsal): toward or at the back of the body; behind.
• Medial: toward or at the midline of the body; on the inner side of.
• Lateral: away from the midline of the body; on the outer side of.
• Proximal: closer to the origin of the body part or the point of attachment of a limb to the body trunk.
• Distal: farther from the origin of a body part or the point of attachment of a limb to the body trunk.
• Superficial (external): toward or at the body surface.
• Deep (internal): away from the body surface; more internal.

Body Planes

• Sagittal plane: divides the body into right and left parts.
• Midsagittal (median) plane: sagittal plane that lies exactly in the midline.
• Frontal (coronal) plane: divides the body into anterior and posterior parts.
• Transverse (horizontal) plane: divides the body into superior and inferior parts.