Microscopy, Basic Cells & Tissues • Language of Anatomy

Overview

These notes synthesise the entire lecture “Introduction to Microscopy, Basic Cells & Tissues + Language of Anatomy”. They are arranged so that each section can be studied independently but also links conceptually to all other sections.

1. Levels of Organisation of the Human Organism

1. Chemical Level

   • Atoms → molecules (water, proteins, DNA, etc.).

   • Foundation of all higher levels; chemical bonding, pH, and ionic composition determine cellular behaviour.

2. Cellular Level

   • Cells = basic living units; arise from molecules.

   • Example cell: smooth-muscle cell (contains actin, myosin, mitochondria, etc.).

3. Tissue Level

   • Similar cells + extracellular matrix (ECM).

   • Histological classification later (§ 8).

4. Organ Level

   • Two or more tissue types combine, e.g. blood vessel contains epithelial, smooth-muscle & connective tissue.

5. Organ-System Level

   • Organs with related functions co-operate (e.g. heart + blood vessels = cardiovascular system).

6. Organismal Level

   • Integrated functioning of 11 organ systems maintains life & homeostasis.

Significance:
• Hierarchical structure explains why disease may originate molecularly yet manifest systemically.
• Clinical assessments often start at system level but treatments can target any level (e.g. gene therapy at chemical level).

2. Definitions

• Anatomy = study of body structure. Etymology from Greek “ana” (up) + “tome” (cut) → literal “cutting up.” Emphasises dissection origins.
• Physiology = study of body function and homeostasis (maintenance of internal variables within narrow ranges).
• The axiom “structure mirrors function” frames all biological reasoning.
– Skull bones are thick/immobile ⇒ protect brain.
– Lung alveoli thin ⇒ maximise diffusion \bigl(\Delta P = k \tfrac{A}{d}\bigr) in Fick’s Law.

3. Subdivisions of Anatomy

1. Surface Anatomy – external forms & markings, assessed visually or by palpation without cutting.

2. Gross Anatomy
   • Studied without microscope; two approaches:
   – Systemic Anatomy (all organs of one system).
   – Regional Anatomy (all structures in one body region).

3. Developmental Anatomy – fertilisation to adult; Embryology = conception → 8 weeks.

4. Histology – microscopic study of tissues (needs microscope).

5. Cytology – study of individual cells.

Connections: Surface & gross anatomy inform surgery & physical exam; histology & cytology underpin pathology.

4. Surface Anatomy

• Practical for landmark-based procedures (e.g. lumbar puncture guided by iliac crest palpation).
• Ethical note: pal­pa­tion respects patient comfort & modesty; communication essential.

5. Anatomical Position, Planes & Sections

5.1 Standard Anatomical Position

1. Erect, head & eyes forward.

2. Feet flat, forward.

3. Arms at side, palms forward.
   All descriptions assume this posture, ensuring universal reference.

5.2 Body Planes

• Sagittal: right/left.
– Midsagittal (median) = equal halves.
– Parasagittal = unequal halves, infinite possibilities.
• Frontal (Coronal): anterior/posterior.
• Transverse (Horizontal): superior/inferior.
• Oblique: angled between any of the above.
Practical use: imaging modalities (CT, MRI) name slices after these planes.

6. Anatomical Terminology

6.1 Regional Terms

Cranial, cervical, cubital, carpal, patellar, etc. (see transcript for complete list).
Used in charting wounds, describing rashes, etc.

6.2 Directional Terms

• Superior/Inferior; Anterior (Ventral)/Posterior (Dorsal); Medial/Lateral/Intermediate; Proximal/Distal; Ipsilateral/Contralateral; Superficial/Deep; Visceral/Parietal.
Clinical correlation: Explaining MRI findings – “lesion is posterior, medial to the optic nerve, deep to the meninges.”

7. Organ Systems – Structure, Function & Interactions

7.1 Integumentary

Skin + accessory (hair, nails, glands).
Functions: protection, temp regulation, excretion (sweat).
Ethical link: largest immunological interface – dermatological drugs must respect systemic absorption.

7.2 Skeletal

Bones & joints; houses hematopoietic cells (→ RBC, WBC, platelets).
Function: support, protection, leverage, mineral storage (Ca^{2+}, PO_4^{3-}).

7.3 Muscular

Skeletal, smooth, cardiac.
Produces movement, posture, thermogenesis (shivering raises temp).
Pathology link: muscular dystrophies illustrate structure–function loss.

7.4 Nervous

CNS (brain, spinal cord) + PNS (nerves, sensory organs).
Rapid electrochemical control; reflex arcs; integrates with endocrine for homeostasis.

7.5 Endocrine

Hormone-secreting glands/cells (pituitary, thyroid, adrenals, pancreatic islets, etc.).
Chemical messengers via blood; slower but widespread effect.
Example: insulin controls glucose \left(\text{target } 70–110\; \text{mg/dL}\right).

7.6 Cardiovascular

Heart + blood + vessels.
Transports gases, nutrients, hormones; regulates temp & water balance (via capillary exchange & plasma osmolarity).
Embryology note: first functional system in embryo (~day 21 heartbeat).

7.7 Digestive

GI tract + accessory glands (liver, gallbladder, salivary).
Mechanical & chemical breakdown, absorption, defecation.
Clinical tie-in: portal circulation links digestive & cardiovascular pathology (e.g. portal hypertension).

7.8 Respiratory

Consist of:

7.9 Urinary

Kidneys, ureters, bladder, urethra.
Excretes nitrogenous wastes, regulates fluid & electrolytes, acid–base.
Nephron anatomy crucial (see histology special topic).

7.10 Reproductive

Male: testes, penis, glands; Female: ovaries, uterus, vagina.
Produces gametes, sex hormones, nurtures embryo (female).
Embryology intimately tied; disruptions cause congenital anomalies.

7.11 Lymphatic & Immunity

Lymph, lymphatics, nodes, tonsils, spleen, thymus.
Returns interstitial fluid to blood, transports fats, immune surveillance.
Clinical correlation: metastasis follows lymphatic drainage patterns.

8. Microscopy & Tools

8.1 Types of Light/Optical Microscopes

• Binocular light microscope, fluorescence, inverted, stereoscope, confocal, light-sheet, atomic-force (AFM).
Each increases resolution or contrast for specific samples.
Ethical angle: minimal sample use, radiation safety in fluorescence.

8.2 Light Microscope Anatomy & Use

Head → ocular (10×), revolving nosepiece → objectives (4×, 10×, 40×, 100× oil).
Condenser focuses light; stage positions specimen; coarse/fine focus knobs.
Protocol: start 4×, coarse focus, centre specimen, progress to higher power, adjust fine focus.

9. Histology – The Four Primary Tissue Types

9.1 Connective Tissue (CT)

• Elements: cells + fibres (collagen, elastic) + ground substance.
• Categories:
– Loose CT (areolar, adipose); many cells, few fibres.
– Dense CT:
* Regular (parallel collagen; tendons).
* Irregular (random collagen; dermis).
– Elastic CT (predominant elastic fibres; large arteries).
• Specialised CT: blood, bone, cartilage.
Significance: ECM changes underpin fibrosis, scurvy (collagen defect), Ehlers-Danlos (elastic defect).

9.2 Epithelial Tissue

• Forms coverings/linings & glands.
• Functions: secretion, protection, absorption, transport, sensation.
• Classification matrix:
– Shapes: squamous, cuboidal, columnar.
– Layers: simple vs stratified (plus pseudostratified & transitional).
Examples:
– Simple squamous – alveoli.
– Stratified squamous – esophagus.
– Transitional – bladder (distensibility).
Clinical: carcinomas arise from epithelia; pattern predicts spread (basement membrane breach).

9.3 Muscle Tissue

1. Skeletal – striated, multinucleated, voluntary, attaches to skeleton.

2. Cardiac – striated, branched, one nucleus, involuntary; intercalated discs for synchronous contraction.

3. Smooth – non-striated, spindle, one nucleus, involuntary; walls of viscera & vessels.
   Actin–myosin interaction drives contraction; Ca^{2+} signalling key.
   Pathology: myocardial infarction = necrosis of cardiac muscle.

9.4 Nervous Tissue

Neurons + neuroglia; specialised for excitability & conductivity.
Functions: control visceral & somatic effectors, process sensory input, cognition.
Clinical: demyelination (MS) disrupts propagation.

10. Developmental Anatomy & Embryology

• Tracks zygote → adult; critical windows where teratogens act.
• Embryology (0–8 weeks): organogenesis; cardiovascular system functional first; neural tube closes by week 4.
Practical: ultrasound dates gestation, detects anomalies.

11. Cytology – Cellular Ultrastructure

• Cell membrane (phospholipid bilayer) – selective permeability.
• Nucleus – control centre; nuclear envelope regulates transport.
• Ribosomes – protein synthesis.
• Endoplasmic reticulum – RER (protein folding), SER (lipid synthesis, detox).
• Golgi apparatus – protein packaging & sorting.
• Mitochondria – ATP production via oxidative phosphorylation
• Lysosomes – digestion of macromolecules; peroxisomes – oxidative detox.
• Cytoskeleton – microtubules, actin, intermediate filaments; maintains shape, motility.
Relation to disease: mitochondrial disorders present multisystemic; lysosomal storage diseases.

12. Integrated Concept – Structure ↔ Function ↔ Homeostasis

• Every anatomical feature is evolutionarily conserved for physiological advantage.
• Homeostatic feedback loops require intact sensory (nervous/endocrine), integrative (CNS), effector (muscle, glands) and structural components.
• Pathology often represents mismatch between structure & required function (e.g. emphysema destroys alveolar walls ⇒ impaired gas exchange).

13. Ethical, Philosophical & Practical Implications

• Historical shift from cadaveric dissection to imaging reflects ethical concerns & technological progress.
• Consent & dignity during dissection; anonymisation of microscope slides from patient biopsies.
• Understanding anatomy underpins safe surgery, radiological interpretation, physiotherapy, and innovations such as 3-D printed organs.

14. Self-Directed Learning & Application

1. Practise identifying planes on peers or models (demonstration exercise).

2. Expand terminology: movements (flexion, extension, abduction, adduction, supination, pronation, dorsiflexion, plantarflexion, circumduction).

3. Apply directional terms in written clinical scenarios.

4. Use microscope protocols to examine histology slides of each tissue type.

15. Summary Checklist (Revision Aid)

✓ Define anatomy vs physiology & relation to homeostasis.
✓ List six structural levels of organisation with examples.
✓ Identify & describe 11 organ systems and key functions.
✓ Distinguish systemic vs regional vs surface anatomy.
✓ Reproduce anatomical position & planes.
✓ Apply all directional & regional terms in context.
✓ Classify tissues & recognise histological images.
✓ Outline light microscope parts & focusing steps.
✓ Trace embryonic development milestones (0-8 weeks).
✓ Relate structure–function examples to clinical conditions.

"Anatomy is not merely about naming parts; it is the vocabulary of medicine, the map for surgery, and the canvas upon which physiology paints the dynamic picture of life."