Anatomy: Structure of Living Organisms

• Anatomy studies the structure of living organisms, including their parts and systems.
• This discipline is fundamental in biology and medicine, providing a framework for understanding the body's function.

Subdivisions of Anatomy

• Gross Anatomy (Macroscopic Anatomy) studies structures visible to the naked eye.
• Microscopic Anatomy (Histology) studies structures at the cellular level using microscopes.
• Developmental Anatomy (Embryology) focuses on organism development from fertilization to birth.
• Systemic Anatomy studies the body by systems, such as the skeletal or nervous system.
• Regional Anatomy studies the body by regions, such as the head, neck, or thorax.
• Surface Anatomy studies internal structures as they relate to the overlying skin surface.
• Comparative Anatomy compares anatomical structures across different species.

Anatomical Position

• Anatomical position is a standardized reference for describing the body.
• In this position, the body is erect, feet slightly apart, palms face forward, and thumbs point away.

Anatomical Planes

• Sagittal plane divides the body into right and left parts.
  • The Midsagittal (median) plane divides the body into equal right and left halves.
  • Parasagittal planes are offset from the midline.
• Frontal (Coronal) plane divides the body into anterior (front) and posterior (back) parts.
• Transverse (Horizontal) plane divides the body into superior (upper) and inferior (lower) parts.

Anatomical Directions

• Superior (cranial) indicates toward the head or upper part of a structure.
• Inferior (caudal) indicates away from the head or toward the lower part of a structure.
• Anterior (ventral) indicates toward the front of the body.
• Posterior (dorsal) indicates toward the back of the body.
• Medial indicates toward the midline of the body.
• Lateral indicates away from the midline of the body.
• Proximal indicates closer to the origin of a body part or point of attachment of a limb.
• Distal indicates farther from the origin of a body part or point of attachment of a limb.
• Superficial (external) indicates toward or at the body surface.
• Deep (internal) indicates away from the body surface.

Body Cavities

• The Dorsal Body Cavity is located near the posterior (dorsal) surface.
  • The Cranial Cavity contains the brain.
  • The Vertebral Cavity contains the spinal cord.
• The Ventral Body Cavity is located near the anterior (ventral) surface.
  • The Thoracic Cavity contains the heart and lungs.
    • Pleural Cavities surround each lung.
    • The Mediastinum contains the heart, esophagus, trachea, and other structures.
  • The Abdominopelvic Cavity contains the abdominal and pelvic organs.
    • The Abdominal Cavity contains the stomach, intestines, liver, and other organs.
    • The Pelvic Cavity contains the bladder, reproductive organs, and rectum.
• Serous Membranes line the ventral body cavities and cover the organs.
  • The Parietal Serosa lines the cavity walls.
  • The Visceral Serosa covers the organs.
  • Serous Fluid lubricates the membranes to reduce friction.

Levels of Structural Organization

• Chemical Level: This includes atoms and molecules.
• Cellular Level: Cells represent the basic structural and functional units.
• Tissue Level: Tissues consist of similar cells performing specific functions.
  • The four basic tissue types are epithelial, connective, muscle, and nervous.
• Organ Level: Organs are composed of two or more tissues and have specific functions.
• System Level: Systems consist of different organs working together.
  • Examples include the digestive, cardiovascular, and nervous systems.
• Organismal Level: This involves the sum total of all structural levels working together.

Tissues

• Epithelial Tissue:
  • It covers body surfaces and lines cavities and ducts.
  • Its functions include protection, absorption, filtration, excretion, secretion, and sensory reception.
  • It is classified by cell shape (squamous, cuboidal, columnar) and layer number (simple, stratified).
• Connective Tissue:
  • It supports, connects, and separates tissues and organs.
  • Types include connective tissue proper (loose and dense), cartilage, bone, and blood.
• Muscle Tissue:
  • It is responsible for movement.
  • The three types are skeletal (voluntary), smooth (involuntary), and cardiac (involuntary).
• Nervous Tissue:
  • It controls and communicates information throughout the body.
  • Main cell types are neurons (transmit signals) and neuroglia (support/protect neurons).

Skeletal System

• This system consists of bones, cartilages, ligaments, and joints.
• Functions include support, protection, movement, mineral storage, and blood cell formation (hematopoiesis).
• Bone Types:
  • Long bones (e.g., femur).
  • Short bones (e.g., carpals).
  • Flat bones (e.g., skull bones).
  • Irregular bones (e.g., vertebrae).
• Bone Structure:
  • Compact bone (dense outer layer).
  • Spongy bone (cancellous bone with trabeculae).
  • Bone markings (surfaces with specific functions).
• Axial Skeleton: Includes the skull, vertebral column, and rib cage.
• Appendicular Skeleton: Includes limb bones and girdles (pectoral and pelvic).

Muscular System

• It consists of skeletal, smooth, and cardiac muscles.
• Functions of Skeletal Muscles:
  • Movement.
  • Posture.
  • Heat generation.
  • Protection of joints.
• Muscle Actions:
  • Agonist (prime mover).
  • Antagonist (opposes the agonist).
  • Synergist (assists the agonist).
• Muscle Attachments:
  • Origin (less movable attachment).
  • Insertion (more movable attachment).

Nervous System

• This system consists of the brain, spinal cord, and nerves.
• Functions include sensory input, integration, and motor output.
• Divisions:
  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): Nerves outside the CNS.
• PNS Subdivisions:
  • Somatic Nervous System: Voluntary control of skeletal muscles.
  • Autonomic Nervous System: Involuntary control of smooth/cardiac muscle and glands.
• Neurons:
  • These are the functional units of the nervous system.
  • Parts include the cell body, dendrites, and axon.
• Neuroglia: These support and protect neurons.

Endocrine System

• This system consists of glands that secrete hormones.
• Functions include regulating body processes via hormones that travel through the bloodstream to target organs.
• Major Glands:
  • Pituitary gland.
  • Thyroid gland.
  • Adrenal glands.
  • Pancreas.
  • Ovaries (females).
  • Testes (males).

Cardiovascular System

• This system consists of the heart, blood vessels, and blood.
• Functions include transporting oxygen, nutrients, hormones, and wastes, as well as temperature regulation and disease protection.
• Heart: Pumps blood.
  • Chambers: Atria (receiving) and ventricles (pumping).
  • Valves: Prevent backflow.
• Blood Vessels:
  • Arteries: Carry blood away from the heart.
  • Veins: Carry blood to the heart.
  • Capillaries: Facilitate exchange between blood and tissues.

Lymphatic System

• This system consists of lymphatic vessels, lymph nodes, and lymphoid organs.
• Functions include returning fluids leaked from blood vessels to the bloodstream, filtering lymph, and immunity.
• Lymphoid Organs:
  • Lymph nodes.
  • Spleen.
  • Thymus.
  • Tonsils.

Respiratory System

• This system consists of the lungs and air passages.
• Functions include gas exchange (oxygen and carbon dioxide) between air and blood.
• Structures:
  • Nose.
  • Pharynx.
  • Larynx.
  • Trachea.
  • Bronchi.
  • Lungs.

Digestive System

• This consists of the gastrointestinal (GI) tract and accessory organs.
• Functions include breaking down food, absorbing nutrients, and eliminating waste.
• Organs:
  • Mouth.
  • Esophagus.
  • Stomach.
  • Small intestine.
  • Large intestine.
  • Liver.
  • Pancreas.
  • Gallbladder.

Urinary System

• This consists of the kidneys, ureters, urinary bladder, and urethra.
• Functions include filtering blood to form urine and regulating blood volume/pressure, electrolyte balance, and acid-base balance.

Reproductive System

• Functions:
  • Produces gametes (sperm and oocytes).
  • Supports offspring development (in females).
  • Produces hormones.
• Male Reproductive System:
  • Testes.
  • Ducts.
  • Accessory glands.
  • Penis.
• Female Reproductive System:
  • Ovaries.
  • Uterine tubes.
  • Uterus.
  • Vagina.
  • External genitalia.
  • Mammary glands.