BIO130 Human Anatomy and Physiology Lab Exam 1 Study Notes

Components and Functions of the Compound Light Microscope

The study of biology at the cellular level requires a complete mastery of the compound light microscope. The physical structure of the microscope is divided into several critical components. The base, labeled as part A, is the heavy bottom part that provides stability. Located on or near the base is the substage light (B) and the power or light switch (C). The intensity of the light is managed by the light voltage control dial or knob (D). The specimen is placed on the stage (E), which often includes a mechanical clamp style for holding slides. Precision movement of the slide is achieved through the mechanical stage slide clamp (F) and the mechanical stage control knobs (G). Beneath the stage, the condenser (H) concentrates light onto the specimen, while the iris diaphragm lever (I) adjusts the amount of light passing through. The height of the condenser can be modified using the condenser height adjustment knob (J).

Focusing requires two distinct mechanisms: the larger circular part known as the coarse focus adjustment knob (K) and the smaller circular part known as the fine focus adjustment knob (L). The upper portion of the microscope includes the head (M), which supports the ocular lenses, and the arm (N), which connects the head to the base. The ocular lens (O) is the tubular part through which the user views the specimen. The revolving nosepiece (P) holds the objective lenses (Q), allowing the user to switch between different levels of magnification.

Microscopic Procedures and Optical Principles

Proper handling and operation of the microscope are essential for maintaining the equipment and obtaining clear images. When transporting the microscope, it must be held with one hand on the arm and the other supporting the base. Before adding or removing a slide, or when beginning work, the lowest power objective (typically the $4x$ scanning objective) should be in place to provide the greatest working distance and prevent damage to the lens or the slide. To optimize the view for the user's specific vision, two ocular adjustments must be made: adjusting the distance between the eyepieces to match the user's interpupillary distance and using the diopter adjustment to account for differences in focus between the left and right eyes. Light intensity can be adjusted via the voltage control dial or by manipulating the iris diaphragm lever.

Working distance is defined as the space between the objective lens and the slide; this distance is smallest on the high-power objective and largest on the scanning objective. When focusing on a stack of three threads, the thread on the top of the stack will be the first to come into focus as the stage moves downward away from the lens. A key feature of modern microscopes is that they are parfocal, meaning that once a specimen is in focus under a lower-power objective, it should remain nearly in focus when switching to a higher-power objective, requiring only minimal adjustment with the fine focus knob.

Quantitative Microscopy: Magnification and Measurements

Total magnification is calculated by multiplying the magnification of the ocular lens by the magnification of the objective lens. Typically, ocular lenses have a magnification of $10x$. When using the $4x$ scanning objective, the total magnification is $40x$. With the $10x$ low-power objective, the total magnification is $100x$, and with the $40x$ high-power objective, the total magnification is $400x$.

Field diameter changes inversely with magnification. If the field diameter ($D$) for a $40x$ objective ($M1$) is $0.455\,mm$, the field diameter for a $4x$ objective ($M2$) can be calculated using the ratio $\frac{M1 \times D1}{M2} = D2$. Metric conversions are also vital: a distance of $1.79\,mm$ is equivalent to $1790\,\mu m$ because $1\,mm = 1000\,\mu m$. To calculate the actual size of an object viewed under the microscope, one must estimate the fraction of the field diameter the object occupies and multiply that fraction by the known field diameter. For example, if a field diameter is $4.65\,mm$ and an object spans half the field, its width is approximately $2.325\,mm$.

Anatomical Landmarks: Anterior and Posterior Regions

Mastery of the language of anatomy requires the identification of specific body landmarks. On the anterior (front) surface, key regions include the forehead (frontal), eye socket (orbital), ear (otic), cheek (buccal), nose (nasal), mouth (oral), chin (mental), neck (cervical), and head (cephalic). The trunk contains the chest (thoracic), breastbone (sternal), breast (mammary), belly button (umbilical), and the region above the waist but below the ribs (abdominal). The pelvic region includes the pelvis, the groin or leg-pit (inguinal), and the genitals (pubic). Upper limb landmarks include the armpit (axillary), arm (brachial), elbow pit (antecubital), forearm (antebrachial), wrist (carpal), palm (palmar), thumb (pollex), and fingers (digital). Lower limb landmarks include the hip (coxal), thigh (femoral), kneecap (patellar), leg or shin (crural), lateral side of the leg (fibular/peroneal), ankle (tarsal), foot (pedal), big toe (hallux), and toes (digital).

On the posterior (back) surface, specific regions include the back of the skull (occipital), shoulder (acromial), shoulder blade (scapular), spine (vertebral), back (dorsal), and lower back (lumbar). The sacral region is at the base of the spine, and the area between the anus and external genitalia is the perineal. The upper limb posterior includes the point of the elbow (olecranal). The lower limb posterior includes the buttocks (gluteal), thigh (femoral), knee pit (popliteal), calf (sural), heel (calcaneal), and sole of the foot (plantar).

Body Orientation, Directional Terminology, and Planes

Directional terms describe the relative positions of body structures. The head is superior (above) to the chest, while the navel is inferior (below) to the chest. The breasts are anterior (front) to the spine, and the buttocks are posterior (back) to the genitalia. The nose is medial (toward the midline) to the ear, while the shoulder is lateral (away from the midline) to the neck. In terms of the spine, the occipital region is superior to the sacral region, and the coccyx is inferior to the cervical region. The spine is on the dorsal surface, and the belly is on the ventral surface. For limbs, the knee is proximal (closer to the attachment point) to the ankle, and the fingers are distal (further from the attachment point) to the elbow. Superficial structures, like the skin, are near the surface, while deep structures, like visceral organs, are further internal.

Sectioning the body occurs along three primary planes: the sagittal plane (longitudinal axis, dividing into left and right), the frontal or coronal plane (longitudinal axis, dividing into anterior and posterior), and the transverse or cross-section plane (dividing into superior and inferior parts).

Body Cavities and Serous Membranes

The body is organized into several cavities. The dorsal cavity contains the cranial cavity (for the brain) and the vertebral/spinal cavity (for the spinal cord). The ventral cavity is divided into the thoracic cavity and the abdominopelvic cavity. Within the thoracic cavity, the mediastinum contains the pericardial cavity (housing the heart) and the pleural cavities (housing the lungs). The abdominopelvic cavity is further divided into the abdominal and pelvic cavities. Serous membranes line these cavities: the parietal layer lines the cavity wall, and the visceral layer covers the organ. Specific examples include the pleura (lungs), pericardium (heart), and peritoneum (abdominopelvic organs).

Cellular Anatomy and Organelle Functions

The cell is the basic functional unit of life, containing various organelles and structures. The plasma membrane (N/P) is the outer phospholipid bilayer. The cytoplasm (C) consists of the cytosol (D) and the organelles (L). The nucleus (K/N) houses the DNA, which exists as loose chromatin (B) or condensed chromosomes (C). The nucleolus (J/M) is the site of ribosome synthesis, and the nuclear envelope (H/K) with nuclear pores (I/L) surrounds the nucleus. Ribosomes (O/Q) are the sites of protein synthesis. The rough endoplasmic reticulum (P/R) is covered in ribosomes for protein production, while the smooth endoplasmic reticulum (Q/T) functions in lipid synthesis. The Golgi apparatus (G) packages proteins for secretion or use in lysosomes (F/H), which contain digestive enzymes. Peroxisomes (M/O) contain oxidases to neutralize radicals. Mitochondria (G/J) produce ATP via oxidation. The cytoskeleton (E) provides structural support, including centrioles (A) for the mitotic spindle, cilia (D) for moving materials, and flagella (F) for cell propulsion. Microvilli (I) increase surface area.

The Cell Cycle and Mitosis

Cell division is categorized into stages. Interphase (A) is the period of growth and DNA replication. Mitosis follows, consisting of Prophase (B), Metaphase (C), Anaphase (D), and Telophase (E). Prophase involves the condensing of chromatin into chromosomes (B) and the formation of the mitotic spindle. During Metaphase, chromosomes align at the equatorial plate. In Anaphase, sister chromatids (joined at the centromere, D) are pulled apart toward opposite poles. Telophase involves the reformation of nuclei. Cytokinesis (F) is the physical division of the cytoplasm, often beginning in late anaphase and concluding after telophase.

Principles of Membrane Transport and Respiration

Diffusion is the movement of molecules from high to low concentration. In experiments, the rate of diffusion is influenced by molecular weight; smaller molecules like potassium permanganate ($mw=158$) diffuse faster than larger ones like methylene blue ($mw=320$). The rate is calculated as distance divided by time (e.g., $18\,mm / 60\,min = 0.3\,mm/min$). Diffusion is faster in liquids than in semi-solids like agar gel.

Osmosis is the diffusion of water across a selectively permeable membrane. In dialysis experiments, Benedict's reagent is used to test for glucose, and silver nitrate is used for NaCl. A dialysis sac containing concentrated solute (like $40\%$ glucose) placed in distilled water will gain weight as water moves in. Tonicity describes the effect of a solution on cell volume: isotonic solutions maintain cell size, hypertonic solutions cause shriveling (crenation), and hypotonic solutions cause swelling and bursting (hemolysis).

Cellular respiration can be studied via fermentation in yeast, which converts glucose into CO2 and ethanol. The rate of $CO_2$ production (calculated in $mL/hr$) is affected by temperature and pH. High temperatures or extreme acidity can denature enzymes, slowing or stopping the reaction. For instance, yeast in $40^{\circ}C$ typically reacts faster than at room temperature, provided the temperature does not reach the point of denaturation.

The Integumentary System

The skin consists of the epidermis (A) and the dermis (B). The epidermis is composed of stratified squamous epithelium with five layers in thick skin: stratum basale (Q), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (A/H). The dermis has a papillary layer (G/H) with dermal papillae (O/C) and a reticular layer (I). Specialized structures include hair follicles (whole structure N/L), hair shafts (M/J), sebaceous glands (H/K), and sudoriferous (sweat) glands (F). Hair consists of a medulla (A), cortex (B), and cuticle (C). Nails include the nail body, root, eponychium (cuticle), and nail bed. Fingerprints exhibit patterns such as arches, loops, and whorls.