Unit 1: Introduction to Anatomy & Physiology

Overview

This unit introduces the foundational concepts of anatomy and physiology, including definitions, levels of organization, anatomical terminology, and the structure of body cavities. Mastery of these topics is essential for understanding the human body and communicating effectively in health sciences.

Anatomy and Physiology: Definitions and Relationships

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.

These two disciplines are complementary: anatomy provides the map, while physiology explains the processes that keep the body alive.

Branches of Anatomy

• Gross Anatomy: Study of structures visible to the naked eye (e.g., heart, lungs, kidneys).

• Surface Anatomy: Study of general form and superficial markings.

• Regional Anatomy: Focuses on anatomical organization of specific areas (e.g., head, trunk).

• Systemic Anatomy: Studies the function of organ systems.

• Developmental Anatomy: Describes changes in form from conception to adulthood.

• Clinical Anatomy: Subspecialties in clinical practice (e.g., pathological anatomy, surgical anatomy).

• Microscopic Anatomy: Deals with structures too small to be seen with the naked eye.

• Cytology: Analysis of internal structures of individual cells.

• Histology: Examination of tissues.

Branches of Physiology

• Cell Physiology: Study of functions of cells.

• System Physiology: Study of physiology of specific organ systems (e.g., pulmonary or cardiac physiology).

• Pathological Physiology: Effects of pathologies on system functions.

Physiology often focuses on events at the cellular or molecular level and is based on physical principles such as electrical currents, blood pressure, and muscle movement.

Levels of Structural Organization

Hierarchy of Organization

The human body is organized from the smallest chemical level to the organism level:

1. Chemical (Molecular) Level: Atoms combine to form molecules (e.g., proteins, carbohydrates).

2. Organelle Level: Molecules combine to make organelles (cellular machinery).

3. Cellular Level: Cells are the structural and functional units of organisms.

4. Tissue Level: Groups of similar cells working together to perform a specific function.

5. Organ Level: Two or more tissues working together to perform specific functions.

6. Organ System Level: Groups of organs interacting to perform a coordinated function.

7. Organism Level: The highest level; all organ systems working together to maintain life.

Humans are multicellular; individual cells must be kept alive for the organism to survive.

Necessary Life Functions

• Integumentary

• Skeletal

• Muscular

• Respiratory

• Digestive

• Cardiovascular

• Urinary

• Lymphatic

• Endocrine

• Nervous

• Reproductive

These systems work together to maintain life in approximately 37.2 trillion cells.

Anatomical Position and Terminology

Standard Anatomical Position

• Body erect

• Feet slightly apart

• Palms facing forward with thumbs pointing away from body

All directional and regional terms are based on this position.

Directional Terms

• Describe one body structure in relation to another (e.g., superior, inferior, anterior, posterior).

Bilateral Symmetry

• External right and left sides of the body are roughly mirror images of one another.

• Important for describing injury to external parts of the body.

Additional Axis-Related Positions

• Longitudinal: Parallel to the axis

• Transverse: At right angles to the axis

• Ipsilateral: Same side

• Contralateral: Opposite side

Regional Terms

• Axial: Head, neck, trunk

• Appendicular: Limbs (arms and legs)

Body Planes and Sections

Body Planes

• Sagittal Plane: Divides the body into left and right sides; produces a sagittal section if cut along this plane.

• Frontal (Coronal) Plane: Divides the body into anterior and posterior sections.

• Transverse (Horizontal) Plane: Divides the body into superior and inferior sections.

• Oblique Section: Result of cuts at angles other than 90 degrees to vertical plane.

Sections

• Named after the plane; e.g., sagittal cut results in a sagittal section.

• Mid-sagittal (Median) Plane: Cut made perfectly on midline.

• Parasagittal Plane: Cut off-centered, not on midline.

Body Cavities and Membranes

Dorsal Body Cavity

• Protects the fragile nervous system.

• Subdivisions:

  • Cranial cavity: Lies in the skull, encases the brain.

  • Vertebral cavity: Lies in the spinal column, encases the spinal cord.

Ventral Body Cavity

• Houses internal organs (viscera).

• Subdivisions:

  • Thoracic cavity:

    • Pleural cavities: Surround lungs

    • Mediastinum: Contains pericardial cavity, surrounds thoracic organs (e.g., esophagus, trachea, thymus, aorta)

    • Pericardial cavity: Encloses heart

  • Abdominopelvic cavity:

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

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

The thoracic and abdominopelvic cavities are divided by the diaphragm.

Retroperitoneal organs (e.g., kidneys, pancreas) are located behind the peritoneum and the muscular wall of the abdominopelvic cavity.

Membranes

• Viscera: Internal organs partially or completely contained in body cavities.

• Serous Membrane: Delicate membrane covering the internal walls of the cavities (parietal layer) and the organs themselves (visceral layer).

Medical Imaging and Examination Techniques

Imaging Techniques

• X-rays: Photographic or digital image of internal composition.

• CAT (CT) Scan: Computed Axial Tomography; creates 3D images using a series of 2D X-rays.

• MRI: Magnetic Resonance Imaging; uses magnetic fields and radio waves to produce detailed images of soft tissue.

• Ultrasound: Uses high-frequency sound waves to produce images of structures; also used to relax muscles.

Scopes and Endoscopes

• Gastroscope: Used to look in the stomach for ulcers or cancers.

• Endoscope: Instrument introduced into the body to view internal parts; may have a light and lens for viewing.

• Other examples: Ophthalmoscope (eye), Bronchoscope (bronchi/lungs), Endoscope (ears), Vaginal speculum (cervix), Proctoscope (rectum), Arthroscope (joints), Laparoscope (abdomen).

Other Means of Testing Body Structures and Functions

• Electroencephalography: Brain activity

• Electrocardiogram: Heart activity

Pathology and Related Terms

Definitions

• Pathology: Study of disease and disorders.

• Symptom: Can be described by affected region (e.g., pain, nausea, vertigo).

• Pathogen: Something that causes a disease (e.g., virus, bacteria).

Body Examination Terms

• Necropsy: To perform an autopsy.

• Vivisection: Practice of performing operations on live animals for research.

• Inspection: To look (e.g., exuts, scars, bleeding).

• Palpation: To feel (e.g., ankle swelling).

• Percussion: To tap to detect hollow or fluid (e.g., pneumonia).

• Auscultation: To listen with a stethoscope (e.g., heart sounds).

• Manipulation: To test range of movement (joint movements).

• Ascites: Abnormal build-up of fluid in the abdomen; more than 25 mL in the peritoneal cavity.

Summary Table: Levels of Structural Organization

Key Equations and Scientific Principles

• Physiology relies on physical principles, such as:

  • Electrical currents

  • Blood pressure

  • Muscle contraction

Example equation for blood pressure:

Additional info:

• Some content inferred for completeness, such as the summary table and example equation.

• Scientific names and terms italicized where appropriate.