Comprehensive Study Guide: Human Anatomy, Chemical Biology, and Cellular Physiology

Anatomical Terminology, Body Cavities, and Serous Membranes

• Anatomical Planes of the Body:

  • Sagittal Plane: A vertical plane dividing the body into right and left portions.

  • Coronal Plane: A vertical plane dividing the body into anterior (front) and posterior (back) portions.

  • Axial / Transverse Plane: A horizontal plane dividing the body into superior (upper) and inferior (lower) portions.

• Directional Terminology:

  • Superior: Toward the head or upper structure.

  • Inferior: Toward the feet or lower structure.

  • Anterior: Toward the front of the body.

  • Posterior: Toward the back of the body.

  • Medial: Toward the midline of the body.

  • Lateral: Away from the midline of the body.

• Subdivisions of the Posterior (Dorsal) Body Cavity:

  • Cranial Cavity: Encased by the skull; houses and protects the brain.

  • Vertebral Cavity: Runs along the vertebral column; houses and protects the spinal cord.

• Subdivisions of the Anterior (Ventral) Body Cavity:

  • Thoracic Cavity: Superior cavity enclosed by the ribs, thoracic muscles, and sternum. Subdivided into:

  • Superior Mediastinum: Central region containing major vascular trunks, esophagus, and trachea.

  • Pleural Cavity: Bilateral cavities containing the lungs.

  • Pericardial Cavity: Located within the mediastinum; surrounds the heart.

  • Diaphragm: Muscular partition dividing the superior thoracic cavity from the inferior abdominopelvic cavity.

  • Abdominopelvic Cavity: Subdivided into:

  • Abdominal Cavity: Contains digestive organs including the stomach, small intestine, large intestine, liver, and spleen.

  • Pelvic Cavity: Inferior cavity containing reproductive organs, urinary bladder, and rectum.

• Serous Membranes (Serosa):

  • Definition: Thin, double-layered membranes lining the walls and organs of closed body cavities (thoracic and abdominopelvic cavities).

  • Pleura: The serous membrane associated with the lungs and pleural cavities.

  • Pericardium: The serous membrane associated with the heart within the pericardial cavity.

  • Peritoneum: The serous membrane associated with the abdominal organs (e.g., stomach, small intestines).

• Anatomical Layers of Serous Membranes (Pericardium Example):

  • Visceral Layer (Visceral Pericardium): Inner layer covering the external surface of the organ directly.

  • Parietal Layer (Parietal Pericardium): Outer layer lining the cavity wall.

  • Serous Cavity (Pericardial Cavity): Fluid-filled potential space/air space between the visceral and parietal layers, acting like a double-walled balloon filled with fluid to reduce friction.

Chemical Organization of the Body and Atomic Structure

• Matter and Mass:

  • Matter: Anything that occupies space and has mass.

  • Mass: A measure of the quantity of matter in an object, standardly measured in grams ($\text{g}$) or kilograms ($\text{kg}$).

  • Elements: Pure chemical substances with unique chemical and physical properties that cannot be broken down into simpler substances through ordinary chemical reactions.

• Chemical Symbols of Elements:

  • Designated by single capital letters or combinations of two letters.

  • Derived from English terms: Carbon ($\text{C}$), Calcium ($\text{Ca}$).

  • Derived from Latin roots:

  • Sodium ($\text{Na}$): Derived from natrium.

  • Potassium ($\text{K}$): Derived from kalium.

• Clinical Terminology for Concentration Imbalances:

  • Prefix Hyper-: Indicates excessive or above-normal levels.

  • Prefix Hypo-: Indicates deficient or below-normal levels.

  • Hypernatremia: Pathological condition characterized by excessive sodium levels in the blood.

  • Hypokalemia: Pathological condition characterized by insufficient potassium levels in the blood.

• Composition of Living Organisms:

  • Major Elements: Four primary elements comprise approximately $96\%$ of human body mass:

  • Oxygen ($\text{O}$)

  • Carbon ($\text{C}$)

  • Hydrogen ($\text{H}$)

  • Nitrogen ($\text{N}$)

  • Trace Elements: Essential elements present in minor quantities (e.g., Calcium [$\text{Ca}$], Phosphorus [$\text{P}$], Iron [$\text{Fe}$]).

• Atomic Structure:

  • Atom: The fundamental, smallest unit of matter retaining all chemical properties of an element.

  • Atomic Regions:

  1. Nucleus: Dense central region containing positively charged Protons ($+\text{1}$ charge) and neutral Neutrons ($\text{0}$ charge).

  2. Electron Cloud: Surrounding area containing negatively charged Electrons ($-\text{1}$ charge) orbiting in defined orbitals/shells.

  • Atomic Number: Defined exclusively by the number of protons in the nucleus; dictates element identity.

  • Neutral Atom Balance: In an uncharged neutral atom, the total number of electrons equals the number of protons.

• Organization of the Periodic Table:

  • Elements are arranged sequentially by increasing atomic number.

  • Groups (Columns) and Periods (Rows) reflect valence shell electron configurations and elemental chemical reactivity.

• Electron Shells and Energy Levels:

  • Electrons occupy distinct energy shells located at varying distances from the nucleus.

  • Shells closer to the nucleus possess lower potential energy levels than outer shells.

  • Energy dynamics: Transitioning an electron to an outer shell requires energy absorption; dropping an electron to an inner shell releases energy.

• Valence Shell and Valence Electrons:

  • Valence Shell: The outermost electron shell of an atom.

  • Valence Electrons: Electrons residing in the valence shell that dictate chemical reactivity and bond formation.

  • Octet Rule: Most biologically critical elements require $8$ valence electrons in their outermost shell to achieve structural stability.

• Ion Formation Mechanisms:

  • Cation Formation (Sodium Example):

  • Sodium ($\text{Na}$) atom: $11$ protons ($11+\text{charge}$), $11$ electrons ($11-\text{charge}$), with $1$ valence electron.

  • To satisfy the octet rule, sodium readily loses its single valence electron, becoming a positively charged cation ($\text{Na}^+$) with $11$ protons and $10$ electrons.

  • Anion Formation (Chlorine / Chloride Example):

  • Chlorine ($\text{Cl}$) atom: $17$ protons ($17+\text{charge}$), $17$ electrons ($17-\text{charge}$), with $7$ valence electrons.

  • Chlorine accepts $1$ electron into its valence shell, forming a negatively charged anion called chloride ($\text{Cl}^-$) with $17$ protons and $18$ electrons.

• Physiological Concentrations of Key Electrolytes:

  • Extracellular Fluid (ECF / Outside Cell):

  • Sodium ($\text{Na}^+$): High concentration ($142\,\text{mM}$).

  • Chloride ($\text{Cl}^-$): High concentration ($103\,\text{mM}$).

  • Calcium ($\text{Ca}^{2+}$): High concentration ($5\,\text{mM}$).

  • Potassium ($\text{K}^+$): Low concentration ($5\,\text{mM}$).

  • Intracellular Fluid (ICF / Inside Cell):

  • Potassium ($\text{K}^+$): High concentration ($148\,\text{mM}$).

  • Organic Anions ($\text{A}^-$): High concentration (large intracellular proteins/molecules).

  • Sodium ($\text{Na}^+$): Low concentration ($10\,\text{mM}$).

  • Chloride ($\text{Cl}^-$): Low concentration ($4\,\text{mM}$).

  • Calcium ($\text{Ca}^{2+}$): Extremely low concentration (<1\,\mu\text{M}).

Organic Compounds and Macronutrients

• Carbon Chemistry and Hydrocarbons:

  • Carbon contains $4$ valence electrons.

  • Rather than gaining or losing electrons, carbon forms stable covalent bonds by sharing four electron pairs.

  • Creates elongated, complex carbon skeletons.

  • Hydrocarbons: Organic molecules composed exclusively of carbon and hydrogen atoms.

• Macronutrients:

  • Definition: Nutrients required by the body in large quantities to furnish metabolic energy and structural framework.

  • Three Primary Classes:

  1. Carbohydrates

  2. Lipids (Fats)

  3. Proteins

• Carbohydrates:

  • Definition: Organic biomolecules composed of carbon, hydrogen, and oxygen (termed "hydrated carbon").

  • Generic Formula: $\left(\text{CH}_2\text{O}\right)_n$

  • Stoichiometry: Hydrogen and oxygen exist in a $2:1$ atomic ratio, identical to water.

  • Saccharides (Sugars) Classifications:

  • Monosaccharides: Single monomer units.

  • Disaccharides: Molecules composed of two covalently bonded monosaccharide monomers.

  • Polysaccharides: Complex polymers composed of hundreds to thousands of monosaccharide units.

• Monosaccharides:

  • Hexose Sugars (Six-Carbon Monosaccharides, $\text{C}_6\text{H}_{12}\text{O}_6$):

  • Glucose: Primary cellular metabolic fuel source.

  • Fructose: Hexose sugar found in fruits.

  • Galactose: Hexose sugar found in dairy products.

  • Pentose Sugars (Five-Carbon Monosaccharides, $\text{C}_5\text{H}_{10}\text{O}_5$ / $\text{C}_5\text{H}_{10}\text{O}_4$):

  • Ribose: Sugar component of RNA.

  • Deoxyribose: Sugar component of DNA.

• Disaccharides:

  • Sucrose (Table Sugar): Composed of Glucose + Fructose.

  • Lactose (Milk Sugar): Composed of Galactose + Glucose.

  • Maltose (Malt Sugar): Composed of Glucose + Glucose.

• Polysaccharides:

  • Starches: Long-chain glucose polymers synthesized by plants; serving as easily digestible plant storage carbohydrates.

  • Glycogen: Highly branched glucose polymer synthesized by animals; stored predominantly in skeletal muscle and liver tissue.

• Lipids:

  • Properties: Water-insoluble organic molecules composed mostly of nonpolar hydrocarbons, rendering them hydrophobic.

  • Major Biological Lipids:

  1. Triglycerides

  2. Phospholipids

  3. Steroids / Sterols

• Triglycerides:

  • Abundance: Most prevalent dietary lipid class and major energy storage form in body tissues.

  • Physical States: Fats (solid at room temperature) and Oils (liquid at room temperature).

  • Molecular Structure: One Glycerol backbone (a three-carbon molecule) linked to three long-chain Fatty Acids.

  • Dehydration Synthesis: Chemical reaction bonding three fatty acids to glycerol with the simultaneous removal and production of three water ($\text{H}_2\text{O}$) molecules.

• Phospholipids:

  • Molecular Structure: Diglyceride structure consisting of a glycerol backbone attached to two nonpolar fatty acid chains and one charged phosphate group (often coupled with a nitrogenous group).

  • Amphipathic Nature:

  • Polar / Hydrophilic Head: Contains the charged phosphate group; attracted to aqueous environments.

  • Nonpolar / Hydrophobic Tail: Contains neutral fatty acid chains; repelled by water.

• Behavior of Phospholipids in Water:

  • Planar Bilayer: Spontaneous alignment into a two-layer sheet roughly $30\,\text{\AA}$ thick, with polar heads facing water and nonpolar tails sequestered inside.

  • Liposomes: Spherical vesicles formed by a lipid bilayer enclosing a central aqueous interior, surrounded by an aqueous exterior.

• Steroids / Sterols:

  • Molecular Structure: Composed of four interlocking hydrocarbon rings.

  • Cholesterol: Precursor molecule from which all body steroids (such as steroid hormones) are synthesized.

• Proteins:

  • Elemental Composition: Always contain Carbon, Hydrogen, Oxygen, Nitrogen ($\text{N}$), and frequently Sulfur ($\text{S}$).

  • Monomer: Amino Acids.

  • Structural and Functional Roles: Structural framework (e.g., Collagen), catalytic enzymes (e.g., Digestive Enzymes), defense (e.g., Antibodies).

  • Fundamental Amino Acid Anatomy:

  • Central Carbon ($\text{C}$) atom.

  • Hydrogen ($\text{H}$) atom.

  • Amino Group ($-\text{NH}_2$ / $+\text{NH}_3$).

  • Carboxyl Group ($-\text{COOH}$ / $-\text{COO}^-$).

  • Variable Side Chain ($\text{R}$ Group): Confers specific chemical properties to each amino acid.

• Structural Hierarchy of Proteins:

  • Peptide: Short chain containing $2$ to $20$ amino acids joined by peptide bonds (e.g., Oxytocin, a $9$-amino-acid hormone).

  • Polypeptide: Chain of more than $20$ amino acids (e.g., Glucagon, a $29$-amino-acid polypeptide).

  • Protein: Functional macromolecule consisting of one or more polypeptides ranging from $50$ to thousands of amino acids folded into complex three-dimensional structures (e.g., Collagen, featuring over $1000$ amino acids arranged in a triple helix).

Cellular Structure and Organization

• The Cell:

  • Fundamental Definition: The basic structural, functional, and biological unit of all living organisms; the smallest unit of life.

  • Physiological Principle: Cell activity dictates tissue and organ performance (e.g., Hepatocytes execute liver metabolic functions; Myocytes shorten to provide muscle contraction).

• Specialized Cell Types:

  • Nerve Cells (Neurons)

  • Muscle Cells: Striated Muscle (voluntary skeletal), Smooth Muscle (involuntary), Cardiac Muscle.

  • Bone Cells (Osteocytes)

  • Gland Cells

  • Blood Cells: Red Blood Cells (Erythrocytes) and White Blood Cells (Leukocytes: Lymphocytes, Monocytes, Neutrophils, Eosinophils, Basophils).

  • Reproductive Cells (Gametes): Sperm and Ovum.

• Animal Cell Subcellular Structures:

  • Plasma Membrane: Outer boundary enclosing cytosol and organelles.

  • Nucleus: Encloses genetic material. Contains:

  • Nucleolus: Site of ribosomal RNA synthesis.

  • Chromatin: DNA and histone protein complex.

  • Nuclear Envelope: Double membrane perforated by Nuclear Pores.

  • Cytoplasm & Cytosol: Intracellular fluid containing organellar machinery.

  • Ribosomes: Protein synthesis sites (free in cytosol or bound to Rough ER).

  • Rough Endoplasmic Reticulum (Rough ER): Membranous network studded with ribosomes; modifies and packages proteins.

  • Smooth Endoplasmic Reticulum (Smooth ER): Lipid and steroid synthesis, carbohydrate metabolism, and calcium storage.

  • Golgi Apparatus: Modifies, sorts, and packages macromolecules for secretion or delivery.

  • Mitochondria: Primary sites of ATP production via cellular respiration.

  • Lysosomes: Digestive organelles containing hydrolytic enzymes to break down debris.

  • Peroxisomes: Neutralize toxins and break down fatty acids.

  • Centrioles: Microtubule-organizing centers active during cell division.

  • Cytoskeleton: Microtubules and Microfilaments providing structural support and movement.

  • Cilia: Motile surface projections driving fluid across the cell membrane.

Structure and Dynamics of the Plasma Membrane

• Plasma Membrane Architecture:

  • Semipermeable selective barrier separating intracellular fluid (ICF) from extracellular fluid (ECF).

  • Arranged as a Phospholipid Bilayer:

  • Hydrophilic Phosphate Heads: Face outward toward aqueous ECF and ICF.

  • Hydrophobic Fatty Acid Tails: Face inward toward the membrane core, establishing a hydrophobic barrier to water-soluble solutes.

• Plasma Membrane Permeability Rules:

  1. Small, Nonpolar Molecules (e.g., Oxygen [$\text{O}_2$], Carbon Dioxide [$\text{CO}_2$]): Easily cross the lipid bilayer by diffusing directly through the hydrophobic core.

  2. Small, Polar Molecules (e.g., Water [$\text{H}_2\text{O}$]): Can traverse the bilayer slowly without protein assistance.

  3. Large, Polar Molecules (e.g., Glucose) and Charged Ions (e.g., $\text{Na}^+$, $\text{K}^+$, $\text{Ca}^{2+}$, $\text{Cl}^-$): Unable to penetrate the nonpolar hydrophobic region without transport proteins.

• Functional Classes of Membrane Proteins:

  • Integral Proteins: Proteins embedded directly within the lipid bilayer, spanning part or all of the membrane (transmembrane proteins).

  • Channel Proteins: Water-filled pores allowing specific solute flux.

  • Carrier Proteins: Transporters undergoing conformational shape changes.

  • Peripheral Proteins: Attached to inner or outer surface surfaces of the membrane.

  • Outer Surface Peripheral Proteins: Serve as cellular identification markers.

  • Inner Surface Peripheral Proteins: Anchor the plasma membrane to the internal cytoskeleton to maintain cell shape.

• Glycocalyx (Glycoproteins and Glycolipids):

  • Glycoproteins: Carbohydrate chains conjugated to integral proteins; function as primary markers for self versus non-self cell recognition.

  • Glycolipids: Carbohydrate chains conjugated to membrane phospholipids; act as blood type surface markers.

  • Glycocalyx: Surface carbohydrate coat formed collectively by glycoproteins and glycolipids.

• Membrane Fluidity Regulation by Cholesterol:

  • Cholesterol molecules insert between adjacent phospholipids within the bilayer.

  • High Temperatures: Restricts fatty acid chain movement, decreasing excessive fluidity and stabilizing the membrane.

  • Low Temperatures: Prevents fatty acid chains from packing tightly, preventing freezing and maintaining membrane fluidity.

Membrane Transport Mechanisms and Tonicity

• Classification of Transport Mechanisms:

  • Passive Transport: Movement of substances across the membrane down their gradient without cellular energy ($\text{ATP}$) expenditure.

  • Active Transport: Energy-requiring ($\text{ATP}$) movement of substances across the membrane, often against their gradient.

• Gradients:

  • Chemical Gradient: Concentration difference of a solute across a membrane.

  • Electrical Gradient: Difference in electrical charge across a membrane.

  • Electrochemical Gradient: Combined chemical and electrical forces driving ion movement.

• Passive Transport Modalities:

  • Simple Diffusion: Unassisted passive movement of lipid-soluble particles, $\text{O}_2$, and $\text{CO}_2$ from high concentration to low concentration directly through the phospholipid bilayer.

  • Facilitated Diffusion: Passive movement of large polar molecules or ions down their concentration gradient via channel or carrier proteins (e.g., movement of glucose via Glucose Transporters [GLUT]).

  • Dynamic Equilibrium: Condition where solute molecules continue crossing the membrane at equal rates in both directions, yielding no net change in concentration over time.

• Ion Channel Biophysics:

  • Pore Selectivity & Electrochemical Exclusion: Channel pores exclude ions based on charge and pore diameter.

  • Channels selective for cations ($\text{Na}^+$, $\text{K}^+$, $\text{Ca}^{2+}$) contain negatively charged amino acid side chains lining the pore.

  • Channels selective for anions ($\text{Cl}^-$) contain positively charged side chains lining the pore.

• Gated Ion Channels:

  • Ligand-Gated Channels: Open or close when a specific chemical signal (ligand) binds to the receptor site (e.g., Acetylcholine [ACh] binding to open cation channels for $\text{Na}^+$, $\text{Ca}^{2+}$, and $\text{K}^+$).

• Mechanically-Gated Channels: Open or close in response to physical membrane deformation (e.g., stretching, mechanical pressure, vibration, touch).

• Voltage-Gated Channels: Open transiently in response to changes in membrane electrical potential.

• Nongated (Leak) Channels:

  • Permanently open pores allowing continuous, passive ion leakage down electrochemical gradients.

  • Resting Membrane Potential Determination: At rest, open potassium ($\text{K}^+$) leak channels far outnumber sodium ($\text{Na}^+$) leak channels. Consequently, passive $\text{K}^+$ efflux is the primary factor establishing resting membrane potential.

• Osmotic Pressure and Osmosis:

  • Osmotic Pressure: The pulling force with which a solution draws water into itself across a semipermeable membrane; directly proportional to dissolved solute particle concentration.

  • Units: Osmoles or milliosmoles ($\text{mOsm}$).

  • Physiological Osmotic Baseline: Human ICF and ECF maintain an osmotic pressure of approximately $300\,\text{mOsm}$.

  • Osmosis: Net diffusion of water across a semipermeable membrane from an area of low osmotic pressure (high water concentration) to high osmotic pressure (low water concentration).

• Tonicity Dynamics:

  • Definition: The ability of an extracellular solution to alter cell shape and volume by inducing fluid movement.

  • Isotonic Solution: Equivalent osmotic pressure to ICF. Zero net water movement; cells retain normal shape and biological function.

  • Hypertonic Solution: Higher osmotic pressure than ICF. Water exits the cell rapidly via osmosis; cells shrivel and shrink (crenation).

  • Hypotonic Solution: Lower osmotic pressure than ICF. Water enters the cell via osmosis; cells swell and risk rupture/bursting (hemolysis).

• Clinical Isotonic Intravenous (IV) Solutions (Target $\approx 300\,\text{mOsm/L}$):

  • $0.9\%$ Sodium Chloride ($0.9\%\,\text{NaCl}$ / Normal Saline): $308\,\text{mOsm/L}$.

  • $5\%$ Dextrose in Water ($\text{D5W}$): $252\,\text{mOsm/L}$.

  • Lactated Ringer's ($\text{LR}$): Contains $\text{Na}^+$, $\text{Cl}^-$, $\text{K}^+$, $\text{Ca}^{2+}$, and lactate (metabolized to bicarbonate): $273\,\text{mOsm/L}$.

  • Clinical Isotonic Equivalence: $0.9\%\,\text{NaCl} \approx 5\%\,\text{D5W} \approx \text{Lactated Ringer's}$.

• Primary Active Transport:

  • Directly uses energy from $\text{ATP}$ hydrolysis to pump solutes against concentration gradients.

  • Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$ ATPase):

  • Stoichiometric Ratio: Expels $3\,\text{Na}^+$ ions out of the cell and imports $2\,\text{K}^+$ ions into the cell per single $\text{ATP}$ consumed.

  • Maintains steep extracellular $\text{Na}^+$ and intracellular $\text{K}^+$ concentration gradients.

• Secondary Active Transport and Cotransport Mechanisms:

  • Secondary Active Transport: Uses the potential energy of an ion gradient created by primary active transport (e.g., $\text{Na}^+$ gradient) to move another substance against its gradient.

  • Antiport (Counter-transport): Transports two distinct solutes in opposite directions across the membrane (e.g., $\text{Na}^+$ moved out while $\text{K}^+$ is moved in).

  • Symport (Cotransport): Transports two distinct solutes in the same direction across the membrane (e.g., $\text{Na}^+$/Glucose symporter dragging glucose into the cell along with $\text{Na}^+$ influx).

• Vesicular Bulk Transport (Endocytosis):

  • Phagocytosis ("Cell Eating"): Endocytosis of large solid particles or invading pathogens by immune cells (forming a phagocytic food vacuole that fuses with lysosomes for enzymatic destruction).

  • Pinocytosis ("Cell Drinking"): Non-specific endocytosis bringing extracellular fluid and dissolved solutes into the cell within micro-vesicles.

Questions & Discussion

• Question: Only sodium was capable of moving and it moved into the cell. The inside of the cell would become _________ __________.

  • Options:

  • A. more positive

  • B. more negative

  • C. less positive

  • D. less negative

  • Correct Answer: A. more positive

  • Physiological Explanation: Sodium ($\text{Na}^+$) carries a net positive charge. Because extracellular sodium concentration ($142\,\text{mM}$) is much higher than intracellular sodium concentration ($10\,\text{mM}$), opening a pathway for sodium allows positive ions to stream down their electrochemical gradient into the cytosol. This influx of positive charge causes the intracellular environment to become more positive (depolarized).