The Human Body: An Orientation – Study Notes for Anatomy & Physiology

An Overview of Anatomy

Definition and Scope

• Anatomy: The study of the structure of the human body.

• Physiology: The study of body function—how body parts work and carry out life-sustaining activities.

Subdisciplines of Anatomy

• Gross anatomy: Study of structures visible to the naked eye.

  • Regional anatomy: Examines all structures in a particular region.

  • Systemic anatomy: Studies body systems one at a time.

  • Surface anatomy: Focuses on external features and their relation to deeper structures.

• Microscopic anatomy (Histology): Study of structures too small to be seen without a microscope.

• Other branches:

  • Developmental anatomy: Study of structural changes throughout life.

  • Embryology: Study of development before birth.

  • Pathological anatomy: Study of structural changes caused by disease.

  • Radiological anatomy: Study of internal structures using imaging techniques.

  • Functional morphology: Study of functional properties of body structures.

The Hierarchy of Structural Organization

Levels of Organization

• Chemical level: Atoms combine to form molecules.

• Cellular level: Cells and their functional subunits.

• Tissue level: Groups of similar cells performing a common function.

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

• Organ system level: Organs that work closely together to accomplish a common purpose.

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

Overview of Organ Systems

Integumentary System

• Forms the external body covering (skin).

• Protects deeper tissues from injury.

• Synthesizes vitamin D.

• Houses cutaneous (pain, pressure, etc.) receptors and sweat/oil glands.

Skeletal System

• Protects and supports body organs.

• Provides a framework for muscles.

• Blood cells are formed within bones.

• Stores minerals (e.g., calcium, phosphorus).

Muscular System

• Allows manipulation of the environment, locomotion, and facial expression.

• Maintains posture.

• Produces heat.

Nervous System

• Fast-acting control system of the body.

• Responds to internal and external changes.

• Activates muscles and glands.

Endocrine System

• Glands secrete hormones that regulate processes such as:

  • Growth

  • Reproduction

  • Nutrient use (metabolism)

Cardiovascular System

• Blood vessels transport blood, which carries oxygen, carbon dioxide, nutrients, and wastes.

• The heart pumps blood through blood vessels.

Lymphatic System/Immunity

• Picks up fluid leaked from blood vessels and returns it to blood.

• Disposes of debris in the lymphatic system.

• Houses white blood cells (lymphocytes).

• Mounts attacks against foreign substances in the body.

Respiratory System

• Keeps blood supplied with oxygen and removes carbon dioxide.

• Gas exchange occurs through the walls of air sacs in the lungs.

Digestive System

• Breaks down food into absorbable units.

• Indigestible foodstuffs are eliminated as feces.

Urinary System

• Eliminates nitrogenous wastes.

• Regulates water, electrolyte, and acid-base balance of the blood.

Male and Female Reproductive Systems

• Overall function is to produce offspring.

• Testes produce sperm and male sex hormones.

• Ovaries produce eggs and female sex hormones.

• Other structures serve as sites for fertilization and development of the fetus.

• Mammary glands produce milk.

Units of Measurement

• The metric system is standard in anatomy.

• Common units:

  • Meter (m)

  • Centimeter (cm)

  • Millimeter (mm)

  • Kilogram (kg)

  • Gram (g)

Anatomical Terminology

• Based on ancient Greek or Latin.

• Provides a standard nomenclature worldwide.

Gross Anatomy—An Introduction

Regional and Directional Terms

• Anatomical position: Standard reference position; body erect, feet together, arms at sides, palms facing forward, thumbs pointing away from the body.

• Regional terms: Designate specific areas within major body divisions (axial and appendicular regions).

• Directional terms: Used to explain the location of one body structure in relation to another.

  • Superior/inferior

  • Anterior (ventral)/posterior (dorsal)

  • Medial/lateral

  • Superficial/deep

Body Planes and Sections

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

  • Midsagittal (median) plane: Lies exactly in the midline.

  • Parasagittal plane: Offset from the midline.

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

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

The Human Body Plan

• Tube-within-a-tube body plan

• Bilateral symmetry

• Dorsal hollow nerve cord

• Notochord and vertebrae

• Segmentation

• Pharyngeal pouches

Body Cavities and Membranes

Dorsal Body Cavity

• Cranial cavity: Contains the brain.

• Vertebral cavity: Contains the spinal cord.

Ventral Body Cavity

• Thoracic cavity: Surrounded by ribs and muscles of the chest.

  • Two pleural cavities (each surrounds a lung).

  • Mediastinum (contains the pericardial cavity, which encloses the heart).

• Abdominopelvic cavity: Contains two parts.

  • Abdominal cavity: Contains the liver, stomach, kidneys, and other organs.

  • Pelvic cavity: Contains the bladder, some reproductive organs, and rectum.

Serous Cavities and Membranes

• Serous cavities are slit-like spaces lined by a serous membrane (pleura, pericardium, peritoneum).

• Serous fluid is produced by both layers of the serous membranes to reduce friction.

Abdominal Quadrants

• The abdomen is divided into four quadrants:

  • Right upper quadrant

  • Left upper quadrant

  • Right lower quadrant

  • Left lower quadrant

Microscopic Anatomy

• Microscopy: Examining small structures through a microscope.

• Light microscopy: Uses light beams for magnification.

• Electron microscopy: Uses beams of electrons for higher magnification.

• Preparing human tissue for microscopy:

  • Specimen is fixed (preserved) and sectioned (sliced thinly).

  • Specimen is stained to distinguish anatomical structures.

  • Acidic stain: Negatively charged dye molecules.

  • Basic stain: Positively charged dye molecules.

• Scanning electron microscopy: Provides three-dimensional images of whole, unsectioned surfaces.

• Artifacts: Minor distortions of preserved tissues; not exactly like living tissues and organs.

Clinical Anatomy—An Introduction to Medical Imaging Techniques

• X-ray: Electromagnetic waves of very short length; best for visualizing bones and abnormal dense structures.

• Advanced X-ray Techniques:

  • Computed tomography (CT): Takes successive X-rays around a person’s full circumference; computer translates recorded information into a detailed picture of the body section.

  • Angiography: Contrast medium highlights vessel structure; digital subtraction angiography (DSA) compares images before and after contrast medium injection to identify blockages.

  • Positron emission tomography (PET): Forms images by detecting radioactive isotopes injected into the body.

  • Sonography (ultrasound imaging): Body is probed with pulses of high-frequency sound waves that echo off the body’s tissues; used to determine the age of a developing fetus.

  • Magnetic resonance imaging (MRI): Produces high-contrast images of soft tissues; distinguishes body tissues based on relative water content.

Example Table: Directional Terms

Term	Definition	Example
Superior (cranial)	Toward the head end or upper part of a structure	The head is superior to the abdomen
Inferior (caudal)	Away from the head end or toward the lower part of a structure	The navel is inferior to the chin
Anterior (ventral)	Toward or at the front of the body	The breastbone is anterior to the spine
Posterior (dorsal)	Toward or at the back of the body	The heart is posterior to the breastbone
Medial	Toward or at the midline of the body	The heart is medial to the arm
Lateral	Away from the midline of the body	The arms are lateral to the chest
Superficial	Toward or at the body surface	The skin is superficial to the skeletal muscles
Deep	Away from the body surface; more internal	The lungs are deep to the skin

Additional info:

• Directional and regional terms are essential for clear communication in clinical and anatomical contexts.

• Medical imaging techniques are continually evolving, providing more detailed and less invasive ways to study the human body.