Foundations of Anatomy & Physiology: Structure, Organization, and Tissue Types

Anatomy and Physiology: Introduction and Branches

Definition and Scope

Anatomy is the study of the structure of living organisms, while physiology focuses on their function. Together, these disciplines explain how the human body is organized and operates.

• Structure refers to the physical organization of body parts.

• Function describes the roles and activities of those parts.

Branches of Anatomy and Physiology

There are multiple specialized branches, each focusing on different aspects of the body:

• Cardiovascular: Heart and blood vessels

• Comparative: Comparison across species

• Cytology: Study of cells

• Developmental: Changes from conception to adulthood

• Endocrinology: Hormones and glands

• Gross Anatomy: Structures visible to the naked eye

• Histology: Microscopic tissue structure

• Immunology: Immune system

• Neurology: Nervous system

• Renal Physiology: Kidneys and urine formation

• Surface Anatomy: External features

• Systemic Physiology: Organ systems

• Altitude, Exercise, Medical, and Reproductive Physiology: Specialized physiological adaptations

Levels of Organization

Hierarchical Structure of the Human Body

The human body is organized into increasingly complex levels:

• Atoms: Basic chemical units

• Molecules: Combinations of atoms (e.g., carbohydrates, proteins, lipids, nucleic acids)

• Cells: Fundamental units of life

• Tissues: Groups of similar cells (epithelial, connective, muscle, nervous)

• Organs: Structures composed of multiple tissue types

• Organ Systems: Groups of organs working together (e.g., integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, immune, respiratory, digestive, urinary, reproductive)

• Organism: The complete living being

The Human Organism Defined (Taxonomy)

Classification of Humans

Humans are classified taxonomically as follows:

Rank	Taxon	Key Features
Kingdom	Animalia	Eukaryotic, heterotrophic animal cells
Phylum	Chordata	Dorsal hollow nerve cord, pharyngeal pouches
Subphylum	Vertebrata	Segmented vertebral column
Class	Mammalia	Mammary glands, hair
Order	Primata	Well-developed brain, prehensile hands
Family	Hominidae	Large cerebrum, bipedal locomotion
Genus	Homo	Flattened face, prominent chin, inferior nostrils
Species	sapiens	Largest cerebrum

Modern humans also possess stereoscopic vision and advanced vocal structures.

Anatomical Position

Standard Reference for Describing the Body

The anatomical position is used as a reference point for anatomical terminology:

• Body erect

• Feet parallel and flat

• Eyes forward

• Arms at sides

• Palms forward

• Fingers down

Planes and Sections

Dividing the Body for Study

• Longitudinal Planes:

  • Frontal (Coronal): Divides body into anterior and posterior parts

  • Sagittal: Divides body into right and left parts

    • Midsagittal: Equal right and left halves

    • Parasagittal: Unequal right and left portions

• Horizontal (Transverse or Cross): Divides body into superior and inferior parts

• Oblique: Cuts at an angle

Directional Terms

Describing Locations and Relationships

• Superior (cranial/cephalic): Toward the head

• Inferior (caudal): Toward the feet

• Anterior (ventral): Toward the front

• Posterior (dorsal): Toward the back

• Medial: Toward the midline

• Lateral: Away from the midline

• Internal (deep): Away from the surface

• External (superficial): Toward the surface

• Proximal: Closer to the point of attachment

• Distal: Farther from the point of attachment

• Visceral: Pertaining to organs

• Median (intermediate): Between two structures

• Parietal: Pertaining to the wall of a body cavity

• Contralateral: Opposite side

• Ipsilateral: Same side

Body Regions

Regional Anatomy

Each part of the body has a specific anatomical name. Students should refer to their text, lab manual, and atlas to learn these terms.

Body Cavities

Major Internal Spaces

• Posterior (Dorsal) Cavities:

  • Cranial: Contains the brain

  • Vertebral: Contains the spinal cord

• Anterior (Ventral) Cavities:

  • Thoracic:

    • Pericardial: Surrounds the heart

    • Pleural: Surrounds the lungs

    • Mediastinum: Central compartment

  • Abdominopelvic:

    • Abdominal: Contains digestive organs

    • Pelvic: Contains reproductive and urinary organs

    • Peritoneal: Surrounds abdominal organs

Membranes

Serous Membranes and Their Functions

Serous membranes line body cavities and cover organs, providing lubrication and protection.

• Pleura: Surrounds lungs (visceral and parietal layers)

• Pericardium: Surrounds heart (visceral and parietal layers)

• Peritoneum: Surrounds abdominal organs (visceral and parietal layers)

• Clinical Note: Infections in these cavities are termed pleurisy (pleural), pericarditis (pericardial), and peritonitis (peritoneal).

Homeostasis

Maintaining Internal Stability

Homeostasis is the process by which the body maintains a stable internal environment despite external changes. This topic is covered in detail later in the course.

Solutions and Concentrations

Basic Chemical Principles in Physiology

• Isotonic, Hypertonic, Hypotonic: Terms describing the relative concentration of solutes in solutions.

• Percent Solution: % = grams solute/100 mL solution

• Mole: Amount of substance containing Avogadro's number ($6.02 \times 10^{23}$) of particles

• Atomic Mass: Molecular weight/mass

• Conversions:

  • moles $\rightarrow$ grams ($\text{grams} = \text{moles} \times \text{MW}$)

  • grams $\rightarrow$ moles ($\text{moles} = \text{grams} / \text{MW}$)

  • moles $\rightarrow$ atoms ($\text{atoms} = \text{moles} \times 6.02 \times 10^{23}$)

  • atoms $\rightarrow$ moles ($\text{moles} = \text{atoms} / 6.02 \times 10^{23}$)

  • grams $\rightarrow$ atoms ($\text{atoms} = \text{grams} / \text{MW} \times 6.02 \times 10^{23}$)

  • atoms $\rightarrow$ grams ($\text{grams} = \text{atoms} / 6.02 \times 10^{23} \times \text{MW}$)

• Molarity (M): Moles solute per liter solution

• Molality (m): Moles solute per kilogram solvent

• Osmole: Unit of osmotic concentration

• Milliosmole (mOsm): 1/1000 of an osmole

• Example: 0.85% NaCl and 5% glucose are isotonic to human cells (both equal 290 mOsm)

Carbohydrates, Lipids, Proteins

Overview of Biological Macromolecules

• Monomers combine to form polymers:

  • Monomer + monomer $\rightarrow$ dimer

  • Dimer + monomer $\rightarrow$ trimer

  • Trimer + monomer $\rightarrow$ tetramer

  • Tetramer + monomer $\rightarrow$ polymer

• Polymers are also called macromolecules or complex molecules.

• Subunits are known as subunits or micromolecules.

Common Reactions in Biochemistry

• Anabolic reactions (building up):

  • Dehydration synthesis: $\text{Monomer} + \text{Monomer} \rightarrow \text{Dimer} + \text{H}_2\text{O}$

• Catabolic reactions (breaking down):

  • Hydrolysis: $\text{Dimer} + \text{H}_2\text{O} \rightarrow \text{Monomer} + \text{Monomer}$

Carbohydrates

• Functions: Energy source, structural support

• Types:

  • Monosaccharides (simple sugars): e.g., glucose ($C_6H_{12}O_6$)

  • Disaccharides: e.g., sucrose ($C_{12}H_{22}O_{11}$)

  • Polysaccharides: e.g., starch, glycogen

Hydrophobic Molecules (Lipids)

• Ordinary lipids:

  • Fats and oils (glycerol + fatty acids)

    • Saturated and unsaturated

    • Trans fats

  • Monoglycerides, diglycerides, triglycerides

  • Beta oxidation and ketoacidosis

• Phospholipids

• Cholesterol

• Steroids

• Prostaglandins

Proteins

• Functions: Enzymes, structural support, transport, signaling

• Monomers: Amino acids

• Structure:

  • Primary: Sequence of amino acids

  • Secondary: Alpha helices and beta sheets

  • Tertiary: 3D folding

  • Quaternary: Multiple polypeptide chains (dimer, trimer, tetramer)

Histology: Study of Tissues

Definition and Types

Histology is the study of tissues at the microscopic level. The four basic tissue types are:

• Epithelial

• Connective

• Muscle

• Nervous

Epithelial Tissue

Characteristics

• Cells are tightly joined, little intercellular space or extracellular matrix

• Avascular (no blood vessels)

• Have a free (apical) surface and a bound surface

• Bound surface rests on basement membrane (glycoproteins, collagen, reticular fibers)

• Located on free surfaces of body, lining organs and cavities

• Functions: Protection, secretion, absorption, excretion, transport, filtration, chemoreception

• Nomenclature: Number of layers (simple, stratified, pseudostratified), shape (squamous, cuboidal, columnar, transitional), surface (plain, ciliated, microvilli)

Types of Epithelial Tissue

• Simple Squamous ET

• Simple Cuboidal ET

• Simple Columnar ET

• Keratined Stratified Squamous ET

• Non-keratinized Stratified Squamous ET

• Stratified Cuboidal ET (rare)

• Stratified Columnar ET (rare)

• Simple Ciliated Columnar ET

• Pseudostratified Ciliated Columnar ET

• Transitional ET

• Glandular ET (e.g., pancreas)

Connective Tissue

Characteristics

• Provides structural and metabolic support

• Manufactures and stores substances

• Highly vascular (except cartilage)

• Abundant intercellular space and matrix

• Not found on free surfaces

• Range from fluid (blood) to compact (bone)

• Named based on fibers produced and concentration

Fibers of Connective Tissue

• Collagen

• Elastic fibers

• Reticular fibers

Cells of Connective Tissue

• Fibroblast

• Reticulocyte

• Chondroblast/Chondrocyte

• Osteoblast/Osteocyte

• Adipocyte

• Mast cell

• Monocyte

• Plasma cell

• Macrophage

Types of Connective Tissue

• Ordinary Connective Tissue:

  • Loose (Areolar) CT

  • Dense Irregular CT

  • Dense Regular (White Fibrous) CT

  • Elastic CT

  • Reticular CT

  • Adipose CT

• Supporting Connective Tissue:

  • Bone CT

  • Hyaline Cartilage CT

  • Elastic Cartilage CT

  • Fibrocartilage CT

• Special Connective Tissue:

  • Vascular CT (blood)

Feedback Mechanisms and Hormones

Regulation of Body Functions

• Positive vs. Negative Feedback: Negative feedback maintains homeostasis; positive feedback amplifies changes.

• Blood Sugar Regulation:

  • Beta cells: Insulin

  • Alpha cells: Glucagon

  • Thyroxine, Cortisone, Epinephrine: Other hormones involved

• Bone Physiology:

  • Cells: Osteoblast (builds bone), Osteoclast (breaks down bone)

  • Hormones: Calcitonin, PTH, Estrogen, Testosterone, Thyroxine, Cortisone

Skin Structure and Function

Functions of Skin

• Body temperature regulation

• Protection

• Perception (sensory)

• Excretion

• Synthesis (e.g., vitamin D)

Skin Layers

• Epidermis

• Dermis

• Hypodermis (Subcutaneous)

Epidermis: Histology and Layers

• Stratum basale: Keratinocytes, melanocytes, tactile (Merkel) cells, non-pigmented dendrocytes

• Stratum spinosum

• Stratum granulosum

• Stratum lucidum (absent in thin skin)

• Stratum corneum

Mitotic activity occurs primarily in the stratum basale.

Additional info: For full mastery, students should consult their textbook, lab manual, and histology slide resources for microscopic identification, locations, and functions of each tissue type and anatomical structure.