CH 1: Science of Anatomy & Physiology

Introduction to Anatomy and Physiology

Anatomy and Physiology Compared

Anatomy and physiology are two closely related branches of biology that study the human body. Understanding both is essential for a comprehensive knowledge of how the body is structured and how it functions.

• Anatomy: The study of the form and structure of the body and its parts.

• Physiology: The study of how the body and its parts work or function.

• Form and function are interrelated: Anatomical structures are designed to perform specific functions.

Example: The structure of the heart (anatomy) enables it to pump blood (physiology).

Anatomy and Physiology Integrated

Integrating the study of anatomy and physiology provides a deeper understanding of the human body. Each discipline informs the other, and knowledge of both is necessary for a complete understanding of health and disease.

• "Form follows function": Anatomical structures are designed to perform their specific functions.

• Physiologists require knowledge of anatomy to understand how structures function.

Levels of Organization in the Human Body

From Simplest to Most Complex

The human body is organized in a hierarchy from the simplest chemical level to the most complex organismal level.

• Atomic particles: Protons, neutrons, electrons

• Chemical level: Atoms, molecules, macromolecules

• Cellular level: Cells, the basic units of life

• Tissue level: Groups of similar cells performing common functions

• Organ level: Two or more tissue types working together

• Organ system level: Related organs working together

• Organismal level: All organ systems functioning together in an individual

Branches of Anatomy

Microscopic Anatomy

Microscopic anatomy examines structures that cannot be seen with the unaided eye. Specimens are examined under a microscope.

• Cytology: The study of body cells and their internal structure.

• Histology: The study of tissues.

Gross (Macroscopic) Anatomy

Gross anatomy investigates structures visible to the unaided eye, often through dissection.

• Systemic anatomy: Studies the anatomy of each body system.

• Regional anatomy: Examines structures in a specific body region.

• Surface anatomy: Focuses on superficial anatomic markings and internal body structures as they relate to the skin surface.

• Comparative anatomy: Examines similarities and differences across species.

• Embryology: Studies developmental changes from conception to birth.

Organ Systems of the Human Body

The human body consists of several organ systems, each with specific functions essential for survival.

• Integumentary system

• Skeletal system

• Muscular system

• Nervous system

• Endocrine system

• Cardiovascular system

• Lymphatic system

• Respiratory system

• Urinary system

• Digestive system

• Male and female reproductive systems

Characteristics of Living Things

All living organisms share certain properties that distinguish them from nonliving matter.

• Organization: Complex structure and order

• Metabolism: Sum of all chemical reactions in the body

  • Anabolism: Small molecules joined to form larger ones

  • Catabolism: Large molecules broken down into smaller ones

• Growth and development: Assimilation of materials, increase in size and specialization

• Responsiveness: Ability to sense and react to stimuli

• Regulation: Ability to adjust internal bodily function to environmental changes

• Homeostasis: Maintenance of a stable internal environment

• Reproduction: Production of new cells for growth, maintenance, repair, and offspring

Homeostasis: Maintaining Internal Stability

Definition and Importance

Homeostasis is the ability of an organism to maintain a consistent internal environment in response to changing internal or external conditions.

• Essential for survival and proper function

• Maintained through complex control systems

Components of Homeostatic Systems

• Receptor: Detects changes in a variable (stimulus)

• Control center: Interprets input from receptor and initiates changes

• Effector: Structure that brings about changes to alter the stimulus

Example: Regulation of body temperature by the nervous system (quick response) or blood calcium levels by the endocrine system (sustained response).

Types of Homeostatic Mechanisms

• Negative feedback: Controls most processes in the body. The resulting action is in the opposite direction of the stimulus, keeping variables within a normal range around a set point.

  • Example: Temperature regulation

• Positive feedback: Occurs less frequently. The stimulus is reinforced to continue moving the variable in the same direction until a climactic event occurs, then the body returns to homeostasis.

  • Examples: Blood clotting, labor contractions, breastfeeding

Establishing Normal Ranges in Clinical Practice

Normal ranges for homeostatic variables are determined by sampling healthy individuals in a population. The normal range includes values for 95% of individuals sampled.

Variable	Normal Range
Body temperature	98.6°F
Blood glucose	80–110 mg/dL
Blood pressure	90–120/60–80 mm Hg

Anatomic Position and Directional Terms

Anatomic Position

The anatomic position is the standard reference position for the body in the study of anatomy.

• Standing upright

• Feet parallel and flat on the floor

• Upper limbs at the sides, palms facing forward

• Head level, eyes looking forward

Directional Terms

Directional terms describe the relative positions of body parts. They are often used in opposing pairs.

Term	Definition
Anterior (ventral)	Toward the front of the body
Posterior (dorsal)	Toward the back of the body
Superior	Above or higher than another part
Inferior	Below or lower than another part
Medial	Toward the midline of the body
Lateral	Away from the midline of the body
Proximal	Closer to the trunk or point of origin
Distal	Farther from the trunk or point of origin

Body Planes

• Coronal (frontal) plane: Divides the body into anterior and posterior parts

• Transverse (horizontal) plane: Divides the body into superior and inferior parts

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

  • Mid-sagittal (median) plane: Divides the body into equal left and right halves

  • Parasagittal plane: Divides the body into unequal left and right portions

Body Cavities and Membranes

Major Body Cavities

• Posterior aspect: Completely encased in bone

  • Cranial cavity: Houses the brain

  • Vertebral canal: Houses the spinal cord

• Ventral cavity: Larger, not completely encased in bone; partitioned by the diaphragm

  • Thoracic cavity: Superior to the diaphragm

  • Abdominopelvic cavity: Inferior to the diaphragm

Serous Membranes

Ventral cavity divisions are lined with serous membranes, which have two layers:

• Parietal layer: Lines the internal surface of the body wall

• Visceral layer: Covers the external surface of organs (viscera)

• Serous cavity: Space between the layers, filled with serous fluid to reduce friction

Abdominopelvic Regions and Quadrants

Nine Regions

The abdominopelvic cavity is divided into nine regions for clinical and anatomical reference:

• Umbilical region: Center, contains the navel

• Epigastric region: Superior to the umbilical region

• Hypogastric region: Inferior to the umbilical region

• Right and left hypochondriac regions: Lateral to the epigastric region

• Right and left lumbar regions: Lateral to the umbilical region

• Right and left iliac regions: Lateral to the hypogastric region

Four Quadrants

The abdominopelvic cavity can also be divided into four quadrants using transverse and midsagittal planes through the umbilicus:

• Right upper quadrant (RUQ)

• Left upper quadrant (LUQ)

• Right lower quadrant (RLQ)

• Left lower quadrant (LLQ)

Clinical Application Example

Case Study: A college student experiences pain that starts near the umbilical region and localizes to the lower right quadrant, with associated symptoms such as nausea and loss of appetite. Examination reveals pain in the right lower quadrant, especially when pressure is applied or during movement.

• Abdominopelvic region affected: Right lower quadrant (RLQ)

• Reason for initial pain near umbilicus: Early appendicitis often starts as referred pain near the umbilicus before localizing to the RLQ as inflammation progresses.

• Most likely organ involved: Appendix