A&P I Exam 1 Comprehensive Study Notes

Foundations of Anatomy and Physiology

• Definitions and Scope:

  • Anatomy: The study of body structures. Anatomy focuses primarily on what something is.
  • Physiology: The study of how body structures function. Physiology focuses primarily on what something does.
  • Core Principle: Structure and function are closely related; the physical form of an organ, tissue, or cell directly dictates and enables its physiological functions.

• Levels of Structural Organization:

  • The structural organization of the human body progresses hierarchically through six specific levels:
    1. Chemical Level: The most fundamental level, composed of atoms and molecules.
    2. Cellular Level: Cells represent the basic structural and functional units of life.
    3. Tissue Level: Consists of groups of similar cells working together to perform a specialized function.
    4. Organ Level: Composed of two or more different tissue types working together to carry out specific, complex functions.
    5. Organ System Level: Consists of multiple related organs working together toward a common physiological goal.
    6. Organism Level: The highest level of organization, representing the complete, integrated living individual.

• Characteristics of Life:

  • Living human organisms share six essential life characteristics:
    • Metabolism: The sum of all chemical reactions occurring within the body.
    • Responsiveness: The ability of an organism to detect changes in either the external or internal environment and respond appropriately.
    • Movement: The physical motion of the whole body, individual organs, single cells, or intracellular and extracellular substances.
    • Growth: An increase in size resulting from an increase in cell size, cell number, or overall body size.
    • Differentiation: The developmental process by which unspecialized precursor cells become specialized cells with specific structural and functional characteristics.
    • Reproduction: The biological process involving either the formation of new cells for tissue growth, repair, or replacement, or the production of a new organism.

Homeostasis and Feedback Mechanisms

• Concept of Homeostasis:

  • Definition: The maintenance of relatively stable internal conditions despite continuous changes in the internal and external environments.
  • Examples of Regulated Internal Conditions:
    • Body temperature
    • Blood glucose concentration
    • Blood pressure
    • Blood $\text{pH}$

• Components of a Feedback System:

  • Homeostatic regulatory loops usually involve three core functional components:
    • Receptor: Sensory structure that detects a specific stimulus or physical/chemical change in the controlled condition and transmits input signals to the control center.
    • Control Center: Evaluates the incoming sensory information, compares it against the established set-point or reference range, and determines the appropriate output response.
    • Effector: Body structure (such as a muscle or gland) that receives output commands from the control center, carries out the physiological response, and alters the status of the controlled condition.

• Sequential Homeostatic Pathway:

  • The homeostatic response mechanism operates through a five-step sequence:
    1. Stimulus: A disruption or change in the regulated condition.
    2. Receptor: Detection of the change and transmission of input.
    3. Control Center: Receipt of input, analysis, and generation of output.
    4. Effector: Receipt of output commands.
    5. Response: Execution of an action that alters the controlled condition.

• Negative Feedback Mechanisms:

  • The most common regulatory feedback mechanism utilized in the human body.
  • Action: Reverses or reduces the direction of the original change to bring the condition back toward its normal baseline or set-point.
  • Examples: Body temperature regulation, blood glucose concentration regulation, and blood pressure regulation.
  • Memory Aid: Negative = negates the change.

• Positive Feedback Mechanisms:

  • A less common feedback mechanism that does not maintain stability directly, but rather produces a rapid, decisive outcome.
  • Action: Amplifies, reinforces, or accelerates the original stimulus, pushing the controlled condition progressively further away from the initial value.
  • Termination: Continues operating in an escalating loop until an outside, specific physiological event halts the cycle.
  • Examples: Labor contractions during childbirth and blood clotting cascade activation.
  • Memory Aid: Positive = pushes the change further.

Anatomical Terminology, Body Planes, and Orientations

• Standard Anatomical Position:
  • A standardized reference stance used to describe anatomical directions and relationships accurately regardless of actual body position.
  • Criteria for Anatomical Position:
    • Body standing completely upright (erect).
    • Head and eyes facing directly forward.
    • Feet flat on the floor and directed forward.
    • Arms positioned at the sides of the torso.
    • Palms facing directly forward (anteriorly).
    • Thumbs pointing away from the body (laterally).
  • All anatomical directional terminology assumes the body is positioned in this exact stance.

• Anatomical Directional Terms:
  • Superior: Toward the head or upper part of a structure; situated above. Example: The heart is superior to the stomach.
  • Inferior: Toward the feet or lower part of a structure; situated below. Example: The stomach is inferior to the heart.
  • Anterior / Ventral: Toward or situated at the front surface of the body. Example: The sternum is anterior to the heart.
  • Posterior / Dorsal: Toward or situated at the back surface of the body. Example: The spine is posterior to the heart.
  • Medial: Nearer to the midline of the body or an organ. Example: The nose is medial to the eyes.
  • Lateral: Farther from the midline of the body; toward the side. Example: The ears are lateral to the nose.
  • Proximal: Closer to the point of attachment of a limb to the trunk, or nearer to the origination of a structure (primarily used for limbs). Example: The elbow is proximal to the wrist.
  • Distal: Farther from the point of attachment of a limb to the trunk, or farther from the origination of a structure. Example: The fingers are distal to the elbow.
  • Superficial: Located closer to or on the surface of the body. Example: The skin is superficial to skeletal muscle.
  • Deep: Located farther from the surface of the body; more internal. Example: Bone is deep to skeletal muscle.
  • Ipsilateral: Located on or affecting the same side of the body.
  • Contralateral: Located on or affecting the opposite side of the body.

• Body Planes:
  • Imaginary flat surfaces that pass through the body to provide anatomical sections:
    • Sagittal Plane: Any vertical plane that divides the body or an organ into right and left portions.
    • Midsagittal Plane (Median Plane): A specific sagittal plane that passes directly through the midline, dividing the body into equal right and left halves.
    • Parasagittal Plane: Any sagittal plane that does not pass through the midline, dividing the body into unequal right and left portions.
    • Frontal / Coronal Plane: A vertical plane oriented perpendicular to a sagittal plane that divides the body or organ into anterior (front) and posterior (back) portions.
    • Transverse / Horizontal Plane: A horizontal plane that divides the body or an organ into superior (upper) and inferior (lower) portions.
    • Oblique Plane: A plane that passes through the body or organ at an angle other than a 90^\t\circ right angle (neither horizontal nor purely vertical).
  • Memory Aids for Planes:
    • Sagittal = left / right
    • Frontal = front / back
    • Transverse = top / bottom

Body Cavities, Abdominopelvic Quadrants, and Serous Membranes

• Dorsal Body Cavity:

  • Located toward the posterior aspect of the body.
  • Surrounds and protects vulnerable organs of the central nervous system.
  • Subdivided into two continuous spaces:
    • Cranial Cavity: Formed by the cranial bones of the skull; encloses and protects the brain.
    • Vertebral (Spinal) Cavity: Formed by the stacked vertebral column; encloses and protects the spinal cord.

• Ventral Body Cavity:

  • Located toward the anterior aspect of the body and houses internal organs collectively referred to as viscera.
  • Subdivided into two principal compartments separated by a skeletal muscle barrier:
    • Thoracic Cavity: Superior subcavity situated above the diaphragm.
      • Mediastinum: Central anatomical compartment within the thoracic cavity extending from the sternum to the vertebral column, containing the heart, major blood vessels, esophagus, and trachea.
      • Pericardial Cavity: Fluid-filled space within the mediastinum that encloses the heart.
      • Pleural Cavities: Two lateral fluid-filled spaces, each surrounding one lung.
    • Diaphragm: The large dome-shaped muscle separating the thoracic cavity from the abdominopelvic cavity; serves as the primary muscle of pulmonary respiration.
    • Abdominopelvic Cavity: Inferior subcavity situated below the diaphragm, extending to the floor of the pelvis. Divided conceptually into:
      • Abdominal Cavity: Superior portion housing primary digestive organs including the stomach, liver, spleen, and intestines.
      • Pelvic Cavity: Inferior portion surrounded by the bony pelvis; houses the urinary bladder, internal reproductive organs, and rectum.

• Abdominopelvic Quadrants:

  • The abdominopelvic cavity is divided into four quadrants by passing a horizontal and a vertical line through the umbilicus:
    • Right Upper Quadrant (RUQ): Contains the majority of the liver, gallbladder, right kidney, and portions of the intestines.
    • Left Upper Quadrant (LUQ): Contains the stomach, spleen, left lobe of the liver, pancreas, left kidney, and portions of the intestines.
    • Right Lower Quadrant (RLQ): Contains the cecum, vermiform appendix, portions of the small intestine, and reproductive organs.
    • Left Lower Quadrant (LLQ): Contains portions of the small and large intestines (sigmoid colon) and reproductive organs.
  • High-Yield Quadrant Organ Associations:
    • $\text{RUQ}$: Liver, gallbladder
    • $\text{LUQ}$: Stomach, spleen
    • $\text{RLQ}$: Appendix
    • $\text{LLQ}$: Left lower abdominal structures

• Serous Membranes (Serosa):

  • Double-layered, thin sheets of tissue associated with specific closed ventral cavities.
  • Mechanism: Secrete a slippery, lubricating serous fluid into the potential space between layers to eliminate friction generated by internal organ movements.
  • Structural Layers:
    • Parietal Layer: The outer layer lining the inner walls of the cavity. Memory Aid: Parietal = perimeter.
    • Visceral Layer: The inner layer adhering directly to the external surfaces of the internal organs. Memory Aid: Visceral = viscera/organs.
  • Specific Serous Membranes:
    • Pleura: Serous membranes associated with the lungs (parietal pleura lines the thoracic wall; visceral pleura covers lung surfaces).
    • Pericardium: Serous membranes associated with the heart (parietal pericardium lines the outer fibrous sac; visceral pericardium covers the myocardium).
    • Peritoneum: Serous membranes associated with the abdominopelvic cavity and its enclosed abdominal viscera.

Chemical Basis of Life: Atoms, Elements, and Chemical Bonds

• Matter and Elements:

  • Matter: Defined as anything that has mass and occupies space ($\text{Matter} = \text{mass} + \text{takes up space}$).
  • Element: A pure chemical substance that cannot be broken down or decomposed into simpler substances by conventional chemical means.

• Elemental Composition of the Human Body:

  • Mnemonic CHNOPS: Represents the essential non-metallic chemical elements making up biological organisms:
    • $\text{C}$: Carbon
    • $\text{H}$: Hydrogen
    • $\text{N}$: Nitrogen
    • $\text{O}$: Oxygen
    • $\text{P}$: Phosphorus
    • $\text{S}$: Sulfur
  • Common Elements and High-Yield Biological Functions:
    • Oxygen ($\text{O}$): Essential for cellular aerobic respiration; constituent of water ($H_2O$) and nearly all organic molecules.
    • Carbon ($\text{C}$): Forms the central structural backbone of all organic macromolecules due to its tetravalent bonding capacity.
    • Hydrogen ($\text{H}$): Major constituent of water, biological fluids, and organic molecules; provides hydrogen ions ($H^+$) that determine acidity.
    • Nitrogen ($\text{N}$): Key component of the amine groups in amino acids (proteins) and nitrogenous bases in nucleic acids ($\text{DNA}$ and $\text{RNA}$).
    • Calcium ($\text{Ca}$): Critical for structural mineralization of bones and teeth, muscle contraction, blood clotting, and neural signaling.
    • Phosphorus ($\text{P}$): Integral component of adenosine triphosphate ($\text{ATP}$), nucleic acid backbones, and bone mineral salts.
    • Sulfur ($\text{S}$): Present in structural side chains of specific amino acids (e.g., cysteine, methionine) and facilitates protein tertiary folding via disulfide bonds.

• Atomic Structure and Subatomic Particles:

  • Atom: The smallest constituent unit of an element that retains all chemical properties characteristic of that element.
  • Subatomic Particles:
    • Protons: Positively charged particles ($+$) residing inside the central atomic nucleus.
    • Neutrons: Electrically neutral particles (charge = $0$) residing inside the central atomic nucleus alongside protons.
    • Electrons: Negatively charged particles ($-$) orbiting outside the nucleus within defined electron orbitals or electron clouds.

• Atomic Properties and Calculations:

  • Atomic Number: The number of protons located within an atom's nucleus; defines elemental identity.
    • In an electrically neutral atom: $\text{Number of protons} = \text{number of electrons}$.
  • Mass Number: The combined count of nucleons within the atomic nucleus.
    • $\text{Mass number} = \text{protons} + \text{neutrons}$
    • $\text{Neutrons} = \text{mass number} - \text{atomic number}$

• Isotopes:

  • Atoms of the same element that possess the identical number of protons (same atomic number) but have differing numbers of neutrons (different mass numbers).
  • Carbon Isotope Examples:
    • $^{12}\text{C}$: Contains $6$ protons and $6$ neutrons ($\text{mass number} = 12$).
    • $^{13}\text{C}$: Contains $6$ protons and $7$ neutrons ($\text{mass number} = 13$).
    • $^{14}\text{C}$: Contains $6$ protons and $8$ neutrons ($\text{mass number} = 14$).

• Ions:

  • An atom or molecule that carries an electrical charge due to an unequal balance of protons and electrons.
  • Cation: A positively charged ion formed when a neutral atom loses one or more valence electrons. Example: $Na^+$ (lost $1\,e^-$). Memory Aid: Lose electrons = positive.
  • Anion: A negatively charged ion formed when a neutral atom gains one or more valence electrons. Example: $Cl^-$ (gained $1\,e^-$). Memory Aid: Gain electrons = negative.

• Chemical Bonds:

  • Ionic Bond: An electrostatic attraction between oppositely charged cations and anions; generally results from the complete transfer of electrons from a metal to a nonmetal. Example: Sodium chloride ($NaCl$), where $Na^+$ bonds electrostatically with $Cl^-$.
  • Covalent Bond: A strong chemical bond established when atoms share one or more pairs of valence electrons.
    • Nonpolar Covalent Bond: Characterized by equal sharing of electrons between atoms with identical or very similar electronegativities (e.g., $H_2$, where electrons are shared equally between $H-H$).
    • Polar Covalent Bond: Characterized by unequal sharing of electrons due to differences in electronegativity; the more electronegative atom pulls shared electrons closer, establishing a partial negative charge ($\delta^-$) on itself and leaving a partial positive charge ($\delta^+$) on the other atom (e.g., $H-O$ bond in water).
  • Hydrogen Bond: A relatively weak intermolecular attraction between an electronegative atom bearing a partial negative charge ($\delta^-$) and a hydrogen atom bearing a partial positive charge ($\delta^+$).
    • Biological Importance: Crucial for stabilizing the unique liquid properties of water, pairing complementary nitrogenous bases in $\text{DNA}$, and maintaining the three-dimensional folding architecture of proteins.

• Properties and Biological Functions of Water ($H_2O$):

  • A bent polar molecule with distinct partial charges ($\delta^-$ on the oxygen atom; $\delta^+$ on the hydrogen atoms).
  • The primary universal solvent for biological chemical reactions.
  • Four Major Bodily Functions:
    • Transport: Dissolves and moves essential nutrients, gases, metabolic wastes, and hormones throughout systemic circulation.
    • Temperature Regulation: Possesses a high heat capacity, absorbing and distributing heat efficiently to buffer internal temperature fluctuations.
    • Chemical Reactions: Acts directly as a reactant or product in critical metabolic processes (e.g., hydrolysis and dehydration synthesis).
    • Lubrication: Forms serous, synovial, and mucus fluids to minimize physical friction across organ interfaces.

• Acids, Bases, Buffers, and the $\text{pH}$ Scale:

  • Acid: A substance that donates hydrogen ions ($H^+$) into aqueous solution according to the Brønsted-Lowry definition. Increases free $[H^+]$; aqueous solutions generally demonstrate a $\text{pH} < 7$.
  • Base: A substance that accepts hydrogen ions ($H^+$) or releases hydroxide ions ($OH^-$) according to the Brønsted-Lowry definition. Decreases free $[H^+]$; aqueous solutions generally demonstrate a $\text{pH} > 7$.
  • The $\text{pH}$ Scale: A logarithmic scale running from $0$ to $14$ measuring relative free $[H^+]$ in solution:
    • $\text{pH} < 7$: Acidic
    • $\text{pH} = 7$: Neutral (pure water, where $[H^+] = [OH^-]$)
    • $\text{pH} > 7$: Basic (alkaline)
    • Logarithmic Nature: Each change of $1$ unit along the $\text{pH}$ scale corresponds to a $10\text{-fold}$ change in hydrogen ion concentration ($[H^+]$). For example, a solution at $\text{pH } 5$ has ten times more $H^+$ than a solution at $\text{pH } 6$.
  • Buffers: Chemical compounds or systems that resist sudden or dramatic shifts in $\text{pH}$ by reversibly binding or releasing $H^+$; essential for maintaining homeostatic $\text{pH}$ within tight biological fluid limits (e.g., blood $\text{pH}$ between $7.35$ and $7.45$).

Biological Macromolecules and Cellular Energy

• Carbohydrates:

  • Composed of carbon, hydrogen, and oxygen, assembled from fundamental sugar units (monosaccharides).
  • Primary source of readily available, immediate cellular energy.
  • High-Yield Carbohydrate Examples:
    • Glucose ($C_6H_{12}O_6$): The primary monosaccharide fuel burned in cellular respiration to produce energy.
    • Glycogen: Highly branched polysaccharide representing the principal storage carbohydrate in animals; stored predominantly within the liver and skeletal muscle tissue.

• Lipids:

  • Hydrophobic, nonpolar organic molecules consisting mostly of hydrocarbon chains.
  • Key Functions:
    • Long-term concentrated energy storage
    • Thermal insulation
    • Physical shock absorption and organ protection
    • Structural framework of cellular membranes
    • Steroid hormone synthesis
  • High-Yield Lipid Classes:
    • Triglycerides: Composed of a glycerol backbone bound to three fatty acids; used for long-term energy storage and insulation.
    • Phospholipids: Amphipathic lipids possessing a polar hydrophilic head and two nonpolar hydrophobic fatty acid tails; form the fundamental structural bilayer of cellular membranes.
    • Steroids / Cholesterol: Lipids structured around a four-ring hydrocarbon backbone; cholesterol stabilizes membrane fluidity and serves as the molecular precursor for steroid hormones (e.g., testosterone, estrogen, cortisol).

• Proteins:

  • Complex polymers constructed from amino acid monomers linked together by covalent peptide bonds ($\text{Amino acids} \rightarrow \text{Protein}$).
  • Major Biological Functions and Specific Examples:
    • Structure: Provide mechanical support across tissues (e.g., collagen, keratin).
    • Movement: Contractile proteins drive physical movement (e.g., actin and myosin in muscle tissue).
    • Transport: Carrier molecules shuttle materials throughout the body (e.g., hemoglobin transports oxygen in erythrocytes).
    • Enzymes: Biological catalysts that accelerate biochemical reactions (e.g., salivary and pancreatic amylase breaks down starches).
    • Receptors: Membrane-bound or intracellular recognition proteins that bind signaling ligands (e.g., hormone receptors).
    • Immunity / Antibodies: Protective defense proteins produced to neutralize foreign antigens (e.g., immunoglobulins).

• Enzymes:

  • Biological catalysts, virtually all of which are specialized globular proteins.
  • Functional Characteristics:
    • Dramatically accelerate the rate of specific biochemical reactions.
    • Function by lowering the activation energy barrier required for a reaction to proceed.
    • Display high substrate specificity.
    • Are not permanently altered, damaged, or consumed during the catalytic reaction cycle, allowing them to be reused repeatedly.

• Nucleic Acids:

  • Polymers composed of repeating nucleotide subunits, each containing a five-carbon sugar, a phosphate group, and a nitrogenous base.
  • Deoxyribonucleic Acid ($\text{DNA}$): Resides in the nucleus; stores hereditary genetic information and contains the molecular blueprints for synthesizing cellular proteins.
  • Ribonucleic Acid ($\text{RNA}$): Transcribes and translates genetic codes; plays an essential functional role in gene expression and ribosomal protein synthesis.

• Adenosine Triphosphate ($\text{ATP}$):

  • The primary chemical energy currency used for immediate energy transfer within all living cells.
  • Structure: Composed of an adenosine molecule (adenine linked to a ribose sugar) attached to three covalently bound phosphate groups ($\text{ATP} = \text{adenosine} + 3\text{ phosphate groups}$).
  • Energy is released when high-energy terminal phosphoanhydride bonds are broken via hydrolysis to yield adenosine diphosphate ($\text{ADP}$) and inorganic phosphate ($P_i$).

Cellular Structure, Organelles, and Membrane Transport

• Basic Cell Architecture:

  • The human cell consists of three primary generalized anatomical components:
    1. Plasma Membrane: Outer flexible boundary separating the intracellular fluid (cytoplasm) from the surrounding extracellular fluid.
    2. Cytoplasm: Cellular contents located between the plasma membrane and the nuclear envelope, comprising cytosol (intracellular fluid) and suspended organelles.
    3. Nucleus: Large, membrane-bound organelle that houses the cell's genome ($\text{DNA}$) and acts as the administrative control center for cellular activities.
       • Nucleolus: Dense non-membrane bound region inside the nucleus responsible for synthesizing ribosomal $\text{RNA}$ ($\text{rRNA}$) and assembling ribosomal subunits.

• Plasma Membrane Structure:

  • Organized as an amphipathic phospholipid bilayer exhibiting selective permeability.
  • Hydrophilic Heads: Phosphate-containing heads carry a charge, are attracted to water (polar), and face outward toward the aqueous intracellular and extracellular environments.
  • Hydrophobic Tails: Two long-chain fatty acid tails per phospholipid avoid water (nonpolar) and project inward toward each other to form a water-resistant hydrophobic interior.

• Cell Organelles and Cytoplasmic Structures:

  • Ribosomes: Non-membrane bound structures comprised of $\text{rRNA}$ and proteins; serve as the cellular sites of protein synthesis (translation).
  • Mitochondria: Double-membrane organelles containing their own mitochondrial $\text{DNA}$; serve as the primary site of aerobic cellular respiration and $\text{ATP}$ generation. Commonly referred to as the powerhouse of the cell.
  • Rough Endoplasmic Reticulum (Rough ER): Extensive membranous network studded on its outer cytosolic surface with attached ribosomes; synthesizes, folds, and processes proteins destined for insertion into cell membranes, packaging into lysosomes, or extracellular exocytosis.
  • Smooth Endoplasmic Reticulum (Smooth ER): Continuous tubular membranous network devoid of ribosomes. Functions include lipid and steroid hormone synthesis, cellular detoxification of drugs and metabolic byproducts, and intracellular calcium ($Ca^{2+}$) storage and release in specialized cells (e.g., sarcoplasmic reticulum of muscle fibers).
  • Golgi Apparatus: Series of flattened, curved membranous sacs (cisternae) that chemically modifies, sorts, packages, and tags proteins and lipids received from the endoplasmic reticulum for targeted vesicular transport. Memory Aid: Golgi = shipping center.
  • Lysosomes: Spherical membrane-enclosed digestive vesicles containing acid hydrolase enzymes; degrade damaged intracellular organelles (autophagy), endocytosed foreign debris, and cellular waste.
  • Cytoskeleton: Complex, dynamic network of filamentous protein strands (microfilaments, intermediate filaments, and microtubules) that establishes structural cell shape, anchors organelles, and facilitates intracellular vesicular transport and whole-cell motility.
  • Centrosome: Primary microtubule-organizing center ($\text{MTOC}$) of the cell, containing a pair of perpendicularly oriented centrioles; organizes the mitotic spindle necessary for chromosome segregation during cellular division.

• Membrane Transport Mechanisms:

  • Passive Transport Processes:
    • Do not directly require cellular metabolic energy or $\text{ATP}$ expenditure.
    • Substances move spontaneously down their concentration gradient or electrochemical gradient (from an area of higher concentration to an area of lower concentration: $\text{high} \rightarrow \text{low}$).
    • Simple Diffusion: Passive movement of small, nonpolar, or lipid-soluble solutes (e.g., $O_2$, $CO_2$) directly across the phospholipid bilayer from high to low concentration without protein assistance.
    • Facilitated Diffusion: Passive movement of charged ions or large polar molecules down their concentration/electrochemical gradient with the assistance of transmembrane channel proteins or carrier proteins; does not consume $\text{ATP}$.
    • Osmosis: The passive net diffusion of water (solvent) molecules across a selectively permeable membrane through specialized channel proteins called aquaporins from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).

• Tonicity and Osmotic Effects on Cells:

  • Tonicity reflects the ability of an extracellular solution to alter the internal volume and shape of a cell by affecting net water movement:
    • Isotonic Solution: Solute concentrations outside and inside the cell are equal. There is no net movement of water across the plasma membrane; the cell maintains its normal volume and shape.
    • Hypotonic Solution: The extracellular environment has a lower solute concentration (and higher water concentration) than the intracellular cytoplasm. Net water moves rapidly into the cell, causing the cell to swell and potentially burst (lysis).
    • Hypertonic Solution: The extracellular environment has a higher solute concentration (and lower water concentration) than the intracellular cytoplasm. Net water moves out of the cell into the extracellular fluid, causing the cell to lose volume, shrink, and shrivel (crenation).