Lab Exam 1

Anatomical Organization and Terminology

• Levels of Structural Organization:

  • Chemical level: Atoms combine to form molecules.

  • Cellular level: Molecules assemble into organelles and cells, the basic structural and functional units of living organisms.

  • Tissue level: Groups of similar cells united to perform a specialized function (epithelial, connective, muscular, nervous).

  • Organ level: Structures composed of two or more tissue types working together for specific complex functions (e.g., skin, duodenum).

  • Organ system level: Consists of related organs with a common function (11 body systems).

  • Organismal level: All organ systems operating together to form a living individual.

• The Eleven Human Organ Systems:

  • Integumentary: Protects the body, regulates temperature, provides sensory reception (skin, hair, nails).

  • Skeletal: Protects and supports organs, provides muscle attachment, stores minerals, produces blood cells.

  • Muscular: Enables movement, maintains posture, produces heat.

  • Nervous: Regulates body activities using electrical impulses (action potentials).

  • Endocrine: Controls metabolic activities via hormone secretion into the bloodstream.

  • Cardiovascular: Transports oxygen, nutrients, wastes, and hormones via blood pumped by the heart.

  • Lymphatic: Defends against infection and disease; returns fluid to the bloodstream.

  • Respiratory: Transfers oxygen from inhaled air to blood and eliminates carbon dioxide.

  • Digestive: Performs physical and chemical breakdown of food, absorbs nutrients, and eliminates solid wastes.

  • Urinary: Filters blood to eliminate liquid wastes, regulates fluid, electrolyte, and acid-base balance.

  • Reproductive: Produces gametes (ova and sperm) and hormones to perpetuate the species.

• Anatomical Position and Directional Pairs:

  • Anatomical position: Standing erect, facing forward, arms at sides, palms facing anteriorly.

  • Superior (cranial) / Inferior (caudal): Above or toward the head / Below or toward the feet.

  • Anterior (ventral) / Posterior (dorsal): Toward the front of the body / Toward the back of the body.

  • Medial / Lateral: Toward the anatomical midline / Away from the anatomical midline.

  • Proximal / Distal: Nearer to the point of attachment of a limb / Farther from the point of attachment.

  • Superficial / Deep: Toward the exterior surface of the body / Inward, farther from the surface.

  • Parietal / Visceral: Pertaining to the outer wall of a cavity / Pertaining to the covering of an internal organ.

• Anatomical Landmarks:

  • Abdominal: Abdomen.

  • Pelvic: Pelvis.

  • Coxal: Hip.

  • Pubic: Anterior pelvis / genital region.

  • Otic: Ear.

  • Frontal: Forehead.

  • Orbital: Eye socket.

  • Nasal: Nose.

  • Cervical: Neck.

  • Thoracic: Chest.

  • Lumbar: Lower back.

  • Sacral: Posterior region between the hips.

  • Axillary: Armpit.

  • Popliteal: Back of the knee.

  • Femoral: Thigh.

  • Plantar: Sole of the foot.

• Body Planes and Sections:

  • Sagittal: Vertical plane dividing the body into unequal right and left parts.

  • Midsagittal (median): Vertical plane passing along the midline dividing the body into equal right and left halves.

  • Frontal (coronal): Vertical plane dividing the body into anterior and posterior portions.

  • Transverse (cross): Horizontal plane dividing the body into superior and inferior portions.

  • Oblique: Angular cut passing through the body at an angle other than a right angle.

• Body Cavities:

  • Cranial cavity: Formed by cranial bones; contains the brain.

  • Thoracic cavity: Chest cavity; contains pleural cavities (surrounding lungs), pericardial cavity (surrounding heart), and the mediastinum (central region between the lungs).

  • Abdominopelvic cavity: Subdivided into the superior abdominal cavity (digestive organs) and inferior pelvic cavity (bladder, internal reproductive organs, rectum).

  • Subdivisions of abdominopelvic cavity:

  • Four quadrants: Right Upper Quadrant (RUQ), Left Upper Quadrant (LUQ), Right Lower Quadrant (RLQ), Left Lower Quadrant (LLQ).

  • Nine regions: Right hypochondriac, epigastric, left hypochondriac, right lumbar (lateral), umbilical, left lumbar (lateral), right iliac (inguinal), hypogastric (pubic), left iliac (inguinal).

Compound Light Microscopy and Cell Analysis

• Microscope Components and Optics:

  • Framework: Base and arm provide structural support; binocular head houses the oculars.

  • Magnification system: Two removable ocular lenses ($10\text{x}$); revolving nosepiece containing four objectives ($4\text{x}$, $10\text{x}$, $40\text{x}$, and $100\text{x}$ oil immersion).

  • Illumination system: Light source, field diaphragm, mirror, and substage condenser with an iris diaphragm to focus light onto the slide and adjust contrast/sharpness.

  • Stage system: Mechanical stage, specimen holder spring clamp, and stage adjustment dials with verniers.

  • Focusing knobs: Coarse focus adjustment knob (for initial focusing at low power) and fine focus adjustment knob (for precise focusing and all high-power viewing).

  • Parfocal property: When an object is focused under one objective, it remains in or near focus when switching to other objectives.

• Calculations:

  • Total microscope magnification:     $\text{Total Magnification} = \text{Ocular Power} \times \text{Objective Power}$

  • $10\text{x}$ ocular $\times$ $4\text{x}$ objective = $40\text{x}$

  • $10\text{x}$ ocular $\times$ $10\text{x}$ objective = $100\text{x}$

  • $10\text{x}$ ocular $\times$ $40\text{x}$ objective = $400\text{x}$

  • $10\text{x}$ ocular $\times$ $100\text{x}$ objective = $1000\text{x}$

  • Field of View Diameters:

  • $4\text{x}$ objective ($40\text{x}$ total) = $4\,\text{mm}$

  • $10\text{x}$ objective ($100\text{x}$ total) = $1.6\,\text{mm}$

  • $40\text{x}$ objective ($400\text{x}$ total) = $0.4\,\text{mm}$

  • $100\text{x}$ objective ($1000\text{x}$ total) = $0.16\,\text{mm}$

  • Drawing Magnification (Scale):     $\text{Drawing Magnification} = \frac{\text{Size of Drawing}}{\text{Actual Size}}$

  • Example: An object extending $\frac{3}{4}$ across a $400\text{x}$ field ($0.40\,\text{mm}$) has an actual size of $0.30\,\text{mm}$. A drawing measuring $60\,\text{mm}$ has a scale of $\frac{60\,\text{mm}}{0.30\,\text{mm}} = 200\text{X}$.

• Eukaryotic Cell Structure:

  • Plasma membrane: Selectively permeable outer phospholipid boundary; regulates substance exchange; can bear microvilli (increase surface area), cilia (fluid movement), or flagella (locomotion).

  • Nucleus: Enclosed by a nuclear membrane; contains nucleoplasm, nucleoli (site of ribosome assembly), and chromatin/chromosomes containing DNA and histones.

  • Cytoplasm: Gel-like or sol-like cytosol suspending subcellular organelles and inclusions.

  • Endomembrane system: Transports and processes macromolecules; comprises the rough endoplasmic reticulum (RER; studded with ribosomes for protein modification), smooth endoplasmic reticulum (SER; lipid synthesis and detoxification), Golgi apparatus (sorting, modification, packaging), lysosomes (hydrolytic digestion), and transport vesicles.

  • Non-endomembrane organelles: Mitochondria (ATP production via cellular respiration), peroxisomes (metabolic oxidations), ribosomes (protein synthesis), centrioles (organize mitotic spindle and asters), and cytoskeleton (microtubules, microfilaments, intermediate filaments).

The Cell Cycle and Mitosis

• Ploidy and Functions of Cell Division:

  • Purposes: Development during embryogenesis, growth of body structures, and tissue repair/replacement.

  • Ploidy ($n$): Number of distinct chromosomes in a species. In humans, $n = 23$.

  • Haploid ($n = 23$): Contains one set of chromosomes (gametes: sperm and ova).

  • Diploid ($2n = 46$): Contains pairs of homologous chromosomes (somatic cells).

• Cell Cycle Phases:

  • Interphase: Non-mitotic interval where the cell metabolizes, grows, and replicates its DNA. Sister chromatids join at a shared centromere.

  • Mitosis (Nuclear Division):

  • Prophase: Chromatin condenses into distinct chromosomes; nuclear membrane breaks down; centriole pairs migrate to opposite poles; mitotic spindle and radial asters assemble from polymerized microtubules; spindle fibers attach to kinetochores/centromeres.

  • Metaphase: Chromosomes align along the metaphase plate perpendicular to the spindle axis.

  • Anaphase: Centromeres split; sister chromatids separate into daughter chromosomes and migrate toward opposite spindle poles via spindle microtubule shortening.

  • Telophase: Chromosomes reach poles, uncoil into diffuse chromatin; mitotic spindle depolymerizes; new nuclear membranes assemble around each set of daughter nuclei.

  • Cytokinesis: Cytoplasmic division, typically occurring concurrently with telophase. A constricting cleavage furrow pinches the mother cell into two genetically identical daughter cells.

Histology: Epithelial and Connective Tissues

• Epithelial Tissue:

  • General characteristics: Cellularity (tightly packed cells, negligible matrix), polarity (apical, lateral, basal surfaces), basement membrane attachment, avascularity (depends on diffusion), and high regenerative capacity.

  • Classification criteria:

  • Layers: Simple (one layer; specialized for absorption, secretion, filtration), stratified (multiple layers; protects against wear and tear), pseudostratified (single layer appearing stratified), transitional (stratified epithelium specialized for distension).

  • Cell shapes: Squamous (flat), cuboidal (cube-like), columnar (tall and cylindrical).

  • Specific classes and anatomical locations:

  • Simple squamous epithelium: Thin diffusion barrier found lining lung alveoli (slide #1) and lining the lumen of blood/lymph vessels (termed endothelium).

  • Simple cuboidal epithelium: Secretory and absorptive ducts; lines kidney tubules (slide #2) and pancreatic ducts (slide #14).

  • Simple columnar epithelium: Lines stomach, intestines (slide #3), and gallbladder; contains microvilli and goblet cells that secrete mucus (mucous epithelium).

  • Simple ciliated columnar epithelium: Lines larger bronchioles; cilia sweep debris-laden mucus upward.

  • Keratinized stratified squamous epithelium: Forms the epidermis of mammalian skin (slides #4 & #5); apical cells accumulate tough, waterproof keratin protein.

  • Non-keratinized stratified squamous epithelium: Lines moist surfaces subjected to abrasion, such as the esophagus (slide #6).

  • Transitional epithelium: Lines the urinary bladder (slide #7); apical cells transition from dome/cuboidal to flattened squamous during luminal distension.

  • Pseudostratified ciliated columnar epithelium: Lines the trachea (slide #8); apical cilia propel mucus.

• Connective Tissue:

  • Composition: Specialized cells surrounded by abundant extracellular matrix (ground substance + extracellular protein fibers: collagen, elastic, or reticular).

  • Subclasses:

  • Loose Connective Tissue Proper:

    • Areolar tissue (slide #9): Widely separated fibroblasts, macrophages, and mast cells with unorganized collagen and elastic fibers; cushions organs and binds epithelia to underlying tissues.

    • Adipose tissue (slide #10): Dominated by adipocytes containing lipid droplets with minimal matrix and no fibers; provides energy storage, thermal insulation, and physical cushioning. Occurs as white adipose and brown adipose (heat generation).

    • Reticular tissue (slide #11): Branching meshwork of dark reticular fibers forming the stroma of lymphoid organs (spleen, lymph nodes, liver).

  • Dense Connective Tissue Proper:

    • Dense regular tissue (slide #13): Densely packed parallel bundles of wavy collagen fibers with sparse fibroblasts; forms tendons (connecting muscle to bone) and ligaments (connecting bone to bone).

    • Dense irregular tissue: Randomly arranged tough collagen fiber networks; found in the dermis of the skin.

    • Dense elastic tissue (slide #12): Abundant coiled, branching elastic fibers allowing recoil; forms walls of large arteries, trachea, and lungs.

  • Fluid Connective Tissue:

    • Blood (slide #17): Consists of erythrocytes (red blood cells for gas transport), leukocytes (white blood cells for immunity), and platelets suspended in liquid plasma without fibers.

  • Supporting Connective Tissue:

    • Hyaline cartilage (slide #8): Chondrocytes housed within lacunae in a firm ground substance containing chondroitin sulfate and invisible/pink collagen fibers; provides smooth, slippery articular surfaces at joints and supports the trachea.

    • Elastic cartilage (slide #15): Chondrocytes in lacunae surrounded by abundant dark elastic fibers; provides flexible structural support.

    • Fibrous cartilage (fibrocartilage): Dense bundles of collagen fibers with fewer chondrocytes; absorbs compressive shock in intervertebral discs, knees, and pubic symphysis.

    • Compact bone (slide #16): Mineralized matrix containing hydroxyapatite arranged in concentric lamellar rings around central canals; osteocytes reside in lacunae.

Questions & Discussion

• Why do higher-power objective lenses have retractable ends?

  • Response: The retractable spring-loaded housing protects both the objective glass lens and the specimen slide from cracking if the lens contacts the coverslip during high-magnification focusing.

• Why does a specimen appear to move in the opposite direction through the oculars compared to the actual stage motion?

  • Response: The compound optical lens system creates an inverted and reversed real intermediate image, causing apparent motion to appear opposite to physical slide displacement.

• Why is isotonic saline used instead of tap water when preparing a live cheek cell mount?

  • Response: Saline matches the osmolarity of human epithelial cells, preventing hypotonic osmotic water influx that would cause cell swelling and lysis.

• What is the common functional adaptation of lung alveolar simple squamous epithelium and capillary endothelium?

  • Response: Both consist of an ultra-thin single cell layer that minimizes the diffusion distance for rapid gas and nutrient exchange between air and blood.

• How do tendons and ligaments structurally differ from loose connective tissues?

  • Response: Tendons and ligaments consist almost entirely of densely packed, parallel collagen fiber bundles with minimal ground substance and few fibroblasts, providing maximal tensile strength along a single direction of stress.

• Why does torn articular hyaline cartilage heal poorly?

  • Response: Cartilage is entirely avascular; nutrients, reparative cells, and growth factors must diffuse slowly through the dense matrix, severely restricting intrinsic repair capacity.