Anatomy and Physiology: An Overview

Introduction to Anatomy and Physiology

• Anatomy studies the structure and relationships between body parts.
• Physiology studies how body parts function to sustain life.
• Anatomy and physiology together provide a comprehensive understanding of the human body.
• These fields rely on principles from chemistry and physics.
• Studying anatomy and physiology offers insights into life processes, disease, recovery, mortality, sex, eating, sleeping, and cognition.

History of Anatomy

• Human dissection was historically a forbidden practice, lasting centuries.
• Galen, a 2nd-century Greek physician, used vivisections on pigs to study human anatomy.
• Da Vinci made anatomical sketches from cadavers until the Pope intervened.
• In the 17th and 18th centuries, public anatomical dissections were conducted by certified anatomists under regulation.
• Grave robbing became a profitable enterprise in Europe until the British Anatomy Act of 1832, which then provided bodies of executed criminals for dissection.
• Currently, anatomy and physiology students learn through dissecting donated cadavers.

Complementarity of Structure and Function

• A structure's function, be it a cell, organ, or organism, is determined by its form.
• Heart valves ensure unidirectional blood flow.
• The strength and hardness of bones enable protection and support of soft tissues.
• The concept applies throughout the body's organizational levels.

Levels of Organization

• Atoms are the most basic units; the human body comprises around 7 octillion atoms.
• Cells, the fundamental units of life, vary in size and shape according to their function.
• Red blood cells are approximately 5 micrometers in diameter.
• Motor neurons can extend up to a meter in length, spanning the entire leg.
• Tissues consist of similar cells, including muscle, membrane, nervous, and connective tissues.
• Organs result from the combination of two or more tissue types to perform specific tasks.
• Organ systems consist of organs working together to perform certain functions.
• The digestive system is an organ system that includes the liver, stomach, and intestines.
• An organism represents the highest level of organization, composed of trillions of cells arranged in a precise manner.

Homeostasis

• Living systems maintain stable internal conditions despite external changes, a process known as homeostasis.
• Survival depends on balancing materials and energy, including blood, water, nutrients, oxygen, body temperature, blood pressure, and waste removal.
• Irreversible loss of homeostasis leads to death.
• Organ failure, hypothermia, suffocation, starvation, and dehydration disrupt internal balance.
• An arterial wound can cause death because it leads to decreased blood pressure and oxygen delivery, which results in the loss of homeostasis.
• While one can survive the loss of a limb, blood pressure, and oxygen delivery are essential for survival.

Anatomical Terminology

• Anatomical position serves as a standard reference: body upright, facing forward, arms at the sides, palms facing forward.
• The sagittal plane divides the body into left and right sections.
• The parasagittal plane runs parallel to the sagittal plane, offset to the side.
• The coronal (frontal) plane divides the body vertically into front and back halves.
• The transverse (horizontal) plane divides the body into upper and lower sections.
• Axial parts consist of the head, neck, and trunk, while appendicular parts comprise the arms and legs.
• Anterior (ventral) refers to the front, and posterior (dorsal) refers to the back.
• Superior (cranial) indicates structures toward the head, whereas inferior (caudal) refers to lower structures.
• Medial describes structures closer to the midline, and lateral refers to structures farther from the midline.
• Proximal indicates structures closer to the trunk's center, while distal indicates those farther from the center.
• For example, the knee is proximal to the ankle, while the wrist is distal to the elbow.