Anatomy & Physiology: Foundations, Cells, Tissues, and Skin

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Anatomy & Physiology: Foundations, Cells, Tissues, and Skin

Introduction to Anatomy & Physiology

Anatomy and physiology are foundational sciences that study the structure and function of the human body. Understanding these disciplines is essential for comprehending how the body maintains health and responds to disease.

Anatomy: Study of body structures, shapes, and positions.
Physiology: Study of how body parts function.

Anatomical Position and Terminology

Standardized anatomical terms are used to describe locations and directions in the body, ensuring clear communication among health professionals.

Anatomical Position: Face forward, feet shoulder-width apart and parallel, arms at sides, palms facing forward.
Directional Terms: Used to describe the location of one body part relative to another (see Table 1.1 in textbook).
Regional Terms: Refer to specific areas of the body (see Table 1.4 in textbook).

Homeostasis

Homeostasis is the process by which the body maintains a stable internal environment despite external changes. It is dynamic, not static, and requires constant regulation.

Key Components:
- Receptor: Monitors changes in the environment.
- Control Center: Determines the set point and response (usually via negative feedback).
- Effector: Carries out the response to restore balance.
Negative Feedback: Most control systems operate via negative feedback (e.g., temperature regulation).

Atoms, Ions, and Isotopes

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons. Ions and isotopes are variations of atoms with different charges or numbers of neutrons.

Electrons: Negatively charged, found in shells around the nucleus.
Protons and Neutrons: Found in the nucleus; protons are positive, neutrons are neutral.
Ions:
- Cations: Positive ions (more protons than electrons).
- Anions: Negative ions (more electrons than protons).
Isotopes: Atoms of the same element with different numbers of neutrons. Some are radioactive and used in medical imaging (e.g., PET scans).

Chemical Bonds

Chemical bonds form when atoms share or transfer electrons, creating molecules essential for life.

Ionic Bonds: Transfer of electrons from one atom to another, creating charged ions (cation and anion).
Covalent Bonds: Sharing of electrons between atoms.
- Nonpolar Covalent: Equal sharing.
- Polar Covalent: Unequal sharing, creating partial charges (e.g., water).
Hydrogen Bonds: Weak attractions between polar molecules, important for water properties and biological molecules.
Chemical Reactions: Can be reversible; some require energy input (endothermic), others release energy (exothermic).

Acids, Bases, Buffers, and pH

Acids and bases are substances that donate or accept protons, respectively. Buffers help maintain pH balance in the body.

Acid: Substance that donates protons (H+).
Base: Substance that accepts protons.
Buffer: Resists changes in pH by neutralizing acids or bases.
pH Scale: Measures hydrogen ion concentration; logarithmic scale.

Key Equation:

Blood pH: 7.35–7.45 (slightly basic); gastric juice is highly acidic at pH 2.

Cells: The Basic Unit of Life

Cells are the smallest structural and functional units of life. They are primarily composed of water and perform all necessary functions for survival.

Eukaryotic Cells: Have a nucleus and membrane-bound organelles.
Prokaryotic Cells: Lack a nucleus; usually bacteria.

Cell Structures and Organelles

Each organelle within a cell has a specific function essential for cell survival and activity.

Nucleus: Contains DNA, controls cell activities.
Ribosomes: Sites of protein synthesis; can be free or attached to rough ER.
Rough Endoplasmic Reticulum (ER): Protein synthesis and export.
Smooth ER: Lipid synthesis, detoxification, calcium storage.
Lysosomes: Contain digestive enzymes for breaking down waste.
Mitochondria: Powerhouse of the cell; produce ATP.
Centrioles: Involved in cell division.
Peroxisomes: Break down hydrogen peroxide.
Golgi Apparatus: Modifies, sorts, and ships proteins.
Secretory Vesicles: Transport proteins to the membrane for release.

Cell Processes

Cells undergo various processes to grow, divide, and maintain function.

Mitosis: Cell division producing identical copies for growth and repair.
Meiosis: Cell division producing gametes (sperm and egg); not identical copies.
DNA Replication: Occurs during the S phase; ensures genetic continuity.
Transcription: DNA to RNA (in nucleus).
Translation: RNA to protein (in cytoplasm).

Central Dogma of Biology:

Types of Tissues in the Body

The human body is composed of four primary tissue types, each with specialized functions.

Epithelial Tissue: Covers surfaces, lines cavities, forms glands; functions in protection, absorption, filtration, secretion.
Connective Tissue: Supports, protects, binds other tissues; includes bone, cartilage, blood, fat.
Muscle Tissue: Enables movement; types include skeletal, smooth, and cardiac.
Nervous Tissue: Conducts electrical impulses; found in brain, spinal cord, nerves.

All tissues are derived from three embryonic layers: ectoderm, mesoderm, and endoderm.

Glands

Glands are specialized epithelial structures that secrete substances.

Exocrine Glands: Release contents onto body surfaces or into body cavities (e.g., sweat, saliva).
Endocrine Glands: Release hormones into the blood to regulate body functions.

Skin and Body Membranes

Membranes protect the body by covering surfaces and lining cavities. They are classified as epithelial or connective tissue membranes.

Epithelial Membranes: Include cutaneous (skin), mucous (line open cavities), and serous (line closed cavities) membranes.
Cutaneous Membrane: The skin; dry, covers the body.
Mucous Membranes: Line cavities open to the exterior (e.g., digestive, respiratory tracts).
Serous Membranes: Line closed cavities; have parietal (lines cavity) and visceral (covers organ) layers.
Connective Tissue Membranes: Synovial membranes; line joint cavities, secrete synovial fluid for lubrication.

Skin Structure and Function

The skin is the largest organ, providing protection, sensation, and regulation of body temperature.

Epidermis: Outermost layer, mostly keratinocytes (produce keratin for waterproofing and protection).
Dermis: Connective tissue, contains blood vessels, nerves, glands, and hair follicles.
Hypodermis: Subcutaneous layer, contains fat and blood vessels.
Skin Layers (from deep to superficial): Dermis, Basale, Spinosum, Granulosum, Corneum (DBSGC).
Cell Turnover: Skin cells slough off from the top layer due to nutrient distance.
Melanin: Pigment produced by melanocytes; two types:
- Pheomelanin: Reddish/yellow pigment.
- Eumelanin: Brown/black pigment.
Merkel Cells: Sensory pressure cells in the stratum basale.

Hair Structure

Hair consists of three concentric layers:

Inner medulla
Central cortex
Outer cuticle

Burn Assessment

Burns are classified by depth (1st, 2nd, 3rd degree) and extent (rule of 9's divides the body into regions representing 9% of total body area each).

Table: Types of Chemical Bonds

Bond Type	Description	Example
Ionic	Transfer of electrons between atoms	NaCl (table salt)
Covalent (Nonpolar)	Equal sharing of electrons	O2 (oxygen gas)
Covalent (Polar)	Unequal sharing of electrons	H2O (water)
Hydrogen	Weak attraction between polar molecules	Between water molecules

Table: Types of Tissues

Tissue Type	Main Function	Location
Epithelial	Protection, absorption, secretion	Skin, lining of organs, glands
Connective	Support, binding, protection	Bone, cartilage, blood, fat
Muscle	Movement	Skeletal muscles, heart, walls of organs
Nervous	Conduct electrical impulses	Brain, spinal cord, nerves

Additional info: Some details, such as the full list of regional and directional terms, are referenced as being in textbook tables and are not fully listed here. The notes have been expanded for clarity and completeness.