Introduction to Anatomy & Physiology

Why Study Anatomy and Physiology?

Anatomy and physiology are foundational sciences for all health professions and biology-based careers. Understanding these subjects enables individuals to make informed health decisions, interpret medical news, and become more knowledgeable about their own bodies.

• Anatomy: The study of internal and external body structures and their physical relationships among other body parts.

• Physiology: The study of how living organisms perform their vital functions.

• Integration: Structure and function are closely related; anatomical features often determine physiological capabilities.

• Applications: Used in clinical practice, research, and personal health management.

Fields of Anatomy and Physiology

• Human Anatomy: Study of the structures of the human body.

• Gross Anatomy (Macroscopic): Examination of large structures visible without a microscope (e.g., cadaver dissection).

• Microscopic Anatomy: Examination of structures only visible with a microscope (e.g., histology – study of tissues).

• Human Physiology: Study of the functions of the human body.

Levels of Organization in the Human Body

Chemical and Cellular Levels

The human body is organized into hierarchical levels, beginning with the chemical level and progressing to the cellular level.

• Chemical Level: Atoms are the smallest stable units of matter; molecules are combinations of atoms (e.g., H2O).

• Cellular Level: Cells are the smallest living units; humans are eukaryotes, meaning their cells contain organelles.

Tissue, Organ, Organ System, and Organism Levels

Higher levels of organization include tissues, organs, organ systems, and the organism itself.

• Tissue Level: Groups of cells working together to perform specific functions; often composed of related cell types.

• Organ Level: Distinct body structures comprised of two or more tissue types that perform specific functions.

• Organ System Level: Groups of organs that interact to perform specific functions.

• Organism Level: The individual living life form.

Organ Systems of the Human Body

Overview of Organ Systems

The human body contains multiple organ systems, each with distinct functions and major organs.

• Integumentary System: Skin, hair, nails; protects against environmental hazards.

• Skeletal System: Bones, cartilages, ligaments, bone marrow; provides support and protection.

• Muscular System: Skeletal muscles; enables movement and generates heat.

• Nervous System: Brain, spinal cord, peripheral nerves, sense organs; directs immediate responses to stimuli.

• Endocrine System: Pituitary glands, thyroid glands, Pancreas, Adrenal glands, gonads; directs long-term changes in other systems.

• Cardiovascular System: Heart, blood, blood vessels; distributes blood, nutrients, and heat.

• Lymphatic System: Spleen, thymus, lymph nodes, lymphatic vessels, tonsils; defends against infection.

• Respiratory System: Lungs, nasal cavities, sinuses, larynx, trachea, bronchi, alveoli; delivers air and removes carbon dioxide.

• Digestive System: Stomach, large intestines, small intestines, liver, teeth, tongue; processes food and absorbs nutrients.

• Urinary System: Kidneys, urinary bladder, urethra, ureters; eliminates waste and regulates water balance.

• Male Reproductive System: Testes, epididymides, seminal vesicles, penis, prostate, scrotum; produces sex cells and hormones.

• Female Reproductive System: Ovaries, uterus, vagina, clitoris, mammary glands, uterine tubes; produces sex cells and hormones.

Anatomical Terminology

Using anatomical terms eliminates ambiguity and ensures clear communication among health professionals.

Anatomical Terms

Anatomical Position: standard anatomical reference position for the human body

• Anatomical Position: Body upright, feet together, hands at sides, palms facing forward.

• Anterior (ventral): Toward the front of the body.

• Posterior (dorsal): Toward the back of the body.

Anatomical Directional Terms

Directional terms describe the locations of structures relative to other structures or locations in the body.

• Anterior (ventral): Towards the front of the body.

  ex. toes are anterior to the heel.

• Posterior (dorsal): Towards the back of the body.

  ex. popliteus is posterior to the patella (the kneecap).

• Superior (cranial): Above or higher than another structure; toward the head.

  ex. the head is superior to the chest

• Inferior (caudal): Below or lower than another structure; toward the feet.

  ex. the pelvis is inferior to the abdomen

• Lateral: Away from the midline of the body.

  ex. pollex (thumb) is lateral to the digits (fingers)

• Medial: Toward the midline of the body.

  ex. hallux (big toe) is the medial toe

• Proximal: Toward the point of attachment of a limb to the body trunk.

  ex. brachium (upper arm) is proximal to the antebrachium (forearm)

• Distal: Away from the point of attachment of a limb to the body trunk.

  ex. the hand is distal to the forearm

• Superficial: At or near the body surface.

  skin is superficial to the bones

• Deep: Toward the interior of the body.

  ex. brain is deep to the skull

• Prone: Face-down orientation.

• Supine: Face-up orientation.

Sectional Anatomy

Section: single view or slice along a plane

- sections through modern medical imaging (x-ray, ultrasound, CT, MRI, PET)

- scan can be only correctly interpreted if the sectional plane is known.

Sectional Planes: imaginary 2-D surface that passes through the body

Sectional anatomy involves viewing the body along specific planes to better understand internal structures. Medical imaging techniques rely on these planes for accurate interpretation.

• Frontal (coronal) plane: Divides the body into anterior and posterior portions.

• Sagittal plane: Divides the body into right and left portions

  • midsagittal is exactly in the middle (equal right and left halves),

  • parasagittal is offset (unequal right and left portions).

• Transverse plane: Divides the body into superior and inferior portions.

Body Cavities

Body cavities are closed, fluid-filled spaces lined by serous membranes. They protect internal organs and allow for changes in organ size and shape.

ex. expansion and contraction of lungs

General Structure and Function

• Serous Membranes (serosa) line the walls of the cavities and cover the surfaces of the enclosed viscera.

  Serous Membranes have two layers:

  • Visceral Layer: cover organs

  • Parietal Layer: lines the cavity walls

• Serous Fluid: Moistens layers and reduces friction during organ movement.

  ex. in-between the visceral and parietal layers of the pericardial cavity is a thin layer of serous fluid (pericardial fluid)

Thoracic Cavity is located deep to the chest wall and separated from the abdominopelvic cavity by the diaphragm. It contains the pleural cavities (lungs), pericardial cavity (surrounds the heart), and the mediastinum (connective tissue supporting major organs).

The Serous Membrane that lines a pleural cavity is called a Pleura.

• Two layers of the pleura:

  • Visceral pleura: covers the lung

  • Varietal pleura: lines the body wall.

The Serous Membrane that lines the pericardial cavity is called the Serous Pericardium.

• Two layers of the serous pericardium:

  • visceral layer: covers the heart

  • parietal layer: lines the mediastinum.

Abdominopelvic cavity is deep to the abdominal and pelvic walls, separated from the thoracic cavity by the diaphragm. It is subdivided into the abdominal cavity (liver, stomach, spleen, intestines) and pelvic cavity (bladder, reproductive organs).

• Peritoneum: Serous membrane lining the peritoneal cavity;

  • parietal peritoneum lines the body wall

  • visceral peritoneum covers digestive organs.

• Retroperitoneal Organs: Organs located between the peritoneal lining and the muscular wall of the abdominal cavity.

  ex. the kidneys and the pancreas

Pelvic Cavity contains the urinary bladder, reproductive organs, and the distal portion of the large intestine. Also constrains the inferior portion of the peritoneal cavity.

Abdominopelvic Quadrants and Regions

Clinicians use quadrants and regions to describe locations of pain, injuries, or abnormalities in the abdominopelvic area.

• Quadrants: Four regions used in clinical practice.

• Regions: More detailed divisions used in anatomical research.

Abdominopelvic regions are often preferred over quadrants.

Homeostasis

Definition and Importance

Homeostasis refers to the continuous physiological processes that maintain a stable internal environment. It is vital for survival, as physiological systems respond to changes to keep conditions within normal ranges.

Homeostatic Regulation: Adjustment of physiological systems to maintain homeostasis.

• Three main parts:

  • Receptor (sensor)

  • Control center (processes information)

  • Effector (responds to commands).

Set Point: Each physiological condition has a set point, or desired value range, around which it fluctuates (e.g., body temerature, blood pressure).

Negative Feedback

Negative feedback mechanisms keep physiological conditions within their set points by opposing deviations from normal values.

ex. Thermoregulation – temperature receptors send information to the hypothalamus, which activates effectors to counteract temperature deviations.

Equation:

Negative feedback: body temperature regulation

Positive Feedback

Positive feedback mechanisms enhance or intensify the original stimulus, often used when a rapid response is needed to restore homeostasis.

ex. Blood clotting – the process continues until a clot is formed.

ex. Labor and delivery – contractions intensify until the newborn is delivered.

• Equation:

Summary Table: Levels of Organization

Summary Table: Homeostatic Regulation

Summary Table: Directional Terms

Summary Table: Sectional Planes

Summary Table: Body Cavities