Chapter 1: The Human Body – An Orientation (Anatomy & Physiology Study Notes)

Chapter 1: The Human Body – An Orientation

Learning Objectives

• Understand the difference and relationship between anatomy and physiology.

• Identify and understand the divisions of anatomy (microscopic and gross).

• Know the levels of organization from atoms to organism.

• Describe the differences of the various organ systems (at a general level).

• Understand the survival needs of organisms.

• Explain the importance of homeostasis and distinguish between positive and negative feedback with examples.

• Describe and identify anatomical directional terms, regional anatomy terms, and body planes.

• Know the body cavities and the two serous membranes of each cavity.

• Identify the four abdominopelvic quadrants and the nine abdominopelvic regions and know the organs they contain.

Form and Function of Anatomy & Physiology

Definitions

• Anatomy: The study of the structure of body parts and their relationships to one another.

• Physiology: The study of the function of body parts; how they work to carry out life-sustaining activities.

Divisions of Anatomy

• Gross (Macroscopic) Anatomy: Study of large, visible structures.

  • Regional anatomy: Study of all structures in a particular area of the body.

  • System anatomy: Study of one body system at a time (e.g., cardiovascular, nervous, muscular).

  • Surface anatomy: Study of internal structures as they relate to the overlying skin (e.g., visible muscle masses or veins).

• Microscopic Anatomy: Study of structures too small to be seen by the naked eye.

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Developmental Anatomy: Study of anatomical and physiological development throughout life.

  • Embryology: Study of developments before birth.

Principle of Complementarity of Structure and Function

Anatomy and physiology are inseparable. Function always reflects structure, and what a structure can do depends on its specific form. This is known as the principle of complementarity of structure and function.

Levels of Structural Organization

The human body is organized in a hierarchy from the simplest to the most complex:

• Chemical level: Atoms combine to form molecules.

• Organelle level: Molecules form organelles, the basic components of cells.

• Cellular level: Cells are made up of organelles and are the smallest units of living things.

• Tissue level: Tissues consist of similar types of cells performing a common function.

• Organ level: Organs are made up of different types of tissues.

• Organ system level: Organ systems consist of different organs that work closely together.

• Organismal level: The human organism is made up of many organ systems.

Necessary Life Functions

• Maintaining boundaries: Separation between internal and external environments (e.g., plasma membranes, skin).

• Movement: Includes activities promoted by the muscular system, such as walking, and movement of substances within the body. Contractility refers to movement at the cellular level.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex).

• Digestion: Breakdown of ingested foodstuffs, followed by absorption of simple molecules into the blood.

• Metabolism: All chemical reactions that occur within body cells, including:

  • Catabolism: Breakdown of molecules.

  • Anabolism: Synthesis of molecules.

• Excretion: Removal of wastes from metabolism and digestion.

• Reproduction: Cellular division for growth or repair, and production of offspring.

• Growth: Increase in size of a body part or of the organism.

Organ Systems Overview

The human body consists of several organ systems, each with specific functions:

• Integumentary System: Protects the body, synthesizes vitamin D, houses receptors and glands.

• Skeletal System: Protects and supports body organs, provides a framework for muscles, forms blood cells, stores minerals.

• Muscular System: Allows manipulation of the environment, locomotion, and facial expression; maintains posture; produces heat.

• Nervous System: Fast-acting control system; responds to internal and external changes.

• Endocrine System: Glands secrete hormones that regulate growth, reproduction, and metabolism.

• Cardiovascular System: Blood vessels transport blood, which carries oxygen, nutrients, wastes, etc.; the heart pumps blood.

• Lymphatic System/Immunity: Picks up fluid leaked from blood vessels, disposes of debris, houses white blood cells, mounts immune response.

• Respiratory System: Keeps blood supplied with oxygen and removes carbon dioxide.

• Digestive System: Breaks down food into absorbable units, eliminates indigestible foodstuffs.

• Urinary System: Eliminates nitrogenous wastes, regulates water, electrolyte, and acid-base balance.

• Male and Female Reproductive Systems: Production of offspring; testes produce sperm and male sex hormones, ovaries produce eggs and female sex hormones.

Survival Needs

• Nutrients: Carbohydrates, proteins, fats, vitamins, and minerals.

• Oxygen: Essential for energy release (ATP production).

• Water: Most abundant chemical in the body; site of chemical reactions.

• Normal body temperature: Necessary for proper metabolic reactions.

• Appropriate atmospheric pressure: Required for adequate breathing and gas exchange.

Homeostasis

Homeostasis is the maintenance of relatively stable internal conditions despite continuous changes in the environment. It is a dynamic state of equilibrium, maintained by all organ systems.

• Variables: Factors that can change (e.g., blood sugar, body temperature, blood volume).

• Control Mechanisms: Involve three components:

  1. Receptor: Monitors environment and responds to stimuli.

  2. Control center: Determines set point, analyzes input, and determines response.

  3. Effector: Carries out the control center's response to the stimulus.

Feedback Mechanisms

• Negative Feedback: Most common; response reduces or shuts off the original stimulus.

  • Example: Regulation of body temperature, regulation of blood glucose by insulin.

• Positive Feedback: Response enhances or exaggerates the original stimulus; usually controls infrequent events.

  • Example: Enhancement of labor contractions by oxytocin, platelet plug formation and blood clotting.

Homeostatic Imbalance

• Disturbance of homeostasis increases risk of disease and contributes to changes associated with aging.

• If negative feedback mechanisms are overwhelmed, destructive positive feedback mechanisms may take over (e.g., heart failure).

Anatomical Terms

Anatomical Position and Directional Terms

• Standard anatomical position: Body erect, feet slightly apart, palms facing forward, thumbs pointing away from the body.

• Directional terms: Describe one body structure in relation to another (e.g., superior/inferior, anterior/posterior, medial/lateral, proximal/distal, superficial/deep).

• Right and left refer to the body being viewed, not the observer.

Body Divisions and Regional Terms

• Axial: Head, neck, and trunk.

• Appendicular: Limbs (arms and legs).

• Regional terms: Designate specific areas within these divisions (e.g., brachial = arm).

Body Planes and Sections

• Sagittal plane: Divides body into right and left parts.

  • Midsagittal (median): Lies on midline.

  • Parasagittal: Not on midline.

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

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

• Oblique section: Cuts made diagonally between horizontal and vertical planes.

Body Cavities and Serous Membranes

Major Body Cavities

• Dorsal body cavity:

  • Cranial cavity: Contains the brain.

  • Vertebral (spinal) cavity: Contains the spinal cord.

• Ventral body cavity:

  • Thoracic cavity: Contains heart and lungs.

    • Pleural cavities: Each surrounds a lung.

    • Mediastinum: Contains pericardial cavity and other thoracic organs.

    • Pericardial cavity: Encloses the heart.

  • Abdominopelvic cavity:

    • Abdominal cavity: Contains stomach, intestines, spleen, liver.

    • Pelvic cavity: Contains urinary bladder, reproductive organs, rectum.

Serous Membranes

• Serosa (serous membrane): Thin, double-layered membranes covering surfaces in the ventral body cavity.

  • Parietal serosa: Lines internal body cavity walls.

  • Visceral serosa: Covers internal organs.

  • Layers separated by serous fluid, reducing friction.

• Named for specific cavities and organs:

  • Pericardium: Heart

  • Pleurae: Lungs

  • Peritoneum: Abdominopelvic cavity

Homeostatic Imbalance of Serous Membranes

• Inflammation (e.g., pleurisy, peritonitis) can cause roughening of membranes, leading to pain and organ dysfunction.

Abdominopelvic Quadrants and Regions

Four Abdominopelvic Quadrants

Quadrant	Major Organs
Right Upper (RUQ)	Liver, gallbladder, right kidney, portions of stomach, small and large intestine
Left Upper (LUQ)	Stomach, spleen, left lobe of liver, pancreas, left kidney, portions of large intestine
Right Lower (RLQ)	Cecum, appendix, portions of small intestine, right ureter, right ovary and spermatic cord
Left Lower (LLQ)	Most of small intestine, portions of large intestine, left ureter, left ovary and spermatic cord

Nine Abdominopelvic Regions

Region	Major Organs
Right hypochondriac	Liver, gallbladder
Epigastric	Stomach, liver, pancreas
Left hypochondriac	Spleen, stomach
Right lumbar	Ascending colon, right kidney
Umbilical	Small intestine, transverse colon
Left lumbar	Descending colon, left kidney
Right iliac (inguinal)	Cecum, appendix
Hypogastric (pubic)	Urinary bladder, sigmoid colon
Left iliac (inguinal)	Initial part of sigmoid colon

Other Body Cavities

• Oral and digestive cavities

• Nasal cavity

• Orbital cavities

• Middle ear cavities

• Synovial cavities: Joint cavities (not exposed to environment)

Sample Review Questions

• Which subdiscipline of anatomy focuses on cells? Cytology

• Which organ system deals with movement? Muscular system

• What are the basic survival needs for organism survival? Nutrients, oxygen, water, normal body temperature, appropriate atmospheric pressure

• What type of plane separates the nose and mouth into superior and inferior structures? Transverse (horizontal) plane

• Which body cavity is associated with the lungs, and what are the names of its serous membranes? Thoracic cavity; pleurae

• In which of the four abdominopelvic quadrants is the gallbladder? Right Upper Quadrant (RUQ)