Overview
This textbook provides a comprehensive visual and functional overview of human histology, including tissue preparation, cellular structures, main tissue types, organ systems, and their microscopic anatomy.
Basic Histologic Methods
- Histology studies tissues using thin, stained sections viewed under light or electron microscopes.
- Tissue preparation includes fixation (usually with formaldehyde), dehydration, embedding in paraffin, sectioning, mounting on slides, and staining.
- Common stains: Hematoxylin (nuclei blue), Eosin (cytoplasm pink), and specialized stains for fibers and specific molecules.
- TEM offers high magnification and resolution for ultrastructure; SEM visualizes 3D surface details.
Cell Structure and Function
- The cell membrane is a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol, key for selective permeability and fluid mosaic structure.
- Organelles: nucleus (with DNA and nucleolus), mitochondria (ATP production), rough and smooth ER (protein/lipid synthesis), Golgi (modification/packaging), lysosomes (digestion), peroxisomes (detoxification), ribosomes (protein synthesis).
- The cytoskeleton includes microfilaments (actin), intermediate filaments, and microtubules for structure and intracellular transport.
- Membrane transport mechanisms: diffusion, facilitated diffusion, active transport, endocytosis, and exocytosis.
Cell Cycle and Division
- Permanent cells (nerves, muscle) don’t divide post-development, stable cells (liver) can regenerate, renewing cells (skin, GI lining) constantly divide.
- Cell cycle: interphase (growth, DNA replication), mitosis (prophase, metaphase, anaphase, telophase), and cytokinesis.
- Meiosis produces haploid gametes (sperm, eggs) for sexual reproduction.
Tissues Overview
Epithelial Tissue
- Covers surfaces, lines cavities, forms glands; avascular with high cell renewal.
- Classified by layers (simple, stratified, pseudostratified) and shape (squamous, cuboidal, columnar).
- Specializations: cilia (movement), microvilli and stereocilia (absorption), junctional complexes (cell adhesion/communication).
- Glands: exocrine (ducts, serous/mucous/mixed types, merocrine/apocrine/holocrine secretion), endocrine (ductless, secrete hormones into blood).
Connective Tissue
- Develops from mesenchyme, includes cells (fibroblasts, adipocytes, macrophages, plasma cells, mast cells) and extracellular matrix (fibers and ground substance).
- Fiber types: collagen (strength), elastic (stretch), reticular (network).
- Loose CT: abundant cells/ground substance; dense CT: more fibers, less ground substance.
- Adipose tissue (white for energy storage, brown for heat generation).
Cartilage and Bone
- Cartilage: hyaline, elastic, and fibrocartilage; avascular, with chondrocytes and matrix.
- Bone: calcified, supports body, site of blood cell formation; contains osteocytes, osteoblasts, osteoclasts.
- Bone growth/remodeling: endochondral and intramembranous ossification.
Muscle Tissue
- Skeletal (striated, voluntary, multinucleated), cardiac (striated, involuntary, intercalated discs), smooth (non-striated, involuntary).
- Sarcomeres are contractile units in striated muscle.
- Cardiac muscle has autorhythmicity and is regulated by the autonomic nervous system.
Nervous Tissue
- Central (brain, spinal cord) and peripheral (nerves, ganglia) nervous systems.
- Neurons (multipolar, bipolar, unipolar) transmit impulses; glial cells support and insulate.
- Myelin sheath insulates axons for faster conduction; synapses enable cell communication.
Organ System Highlights
Circulatory System
- Heart pumps blood through arteries, capillaries, and veins; walls consist of tunica intima, media, and adventitia.
- Capillaries (continuous, fenestrated, sinusoidal) are sites of exchange; lymphatic system returns interstitial fluid to blood.
Immune & Lymphatic System
- Lymphoid organs: lymph nodes, spleen, thymus; lymphocytes (T and B), NK cells, and APCs mediate immunity.
- Innate immunity is rapid/nonspecific; adaptive immunity provides targeted and memory-based defense.
Integumentary System
- Skin: stratified keratinized squamous epithelium (epidermis); underlying dermis (connective tissue).
- Appendages: hair, nails, sweat and sebaceous glands.
- Functions: protection, thermoregulation, sensation, vitamin D synthesis.
Digestive System
- Layers: mucosa, submucosa, muscularis externa, serosa/adventitia.
- Specialized regions: oral cavity, esophagus, stomach, intestines, accessory glands (liver, pancreas, gallbladder).
- Glands secrete digestive enzymes, mucus, or hormones.
Urinary System
- Kidneys filter blood through nephrons: glomerular filtration, tubular reabsorption/secretion, urine concentration.
- Maintains fluid, electrolyte, and acid-base balance; regulates blood pressure via renin.
Endocrine System
- Ductless glands (pituitary, thyroid, parathyroid, adrenal, pancreas, gonads) secrete hormones into blood.
- Hormones regulate metabolism, growth, reproduction, homeostasis.
Reproductive System
- Male: testes (spermogenesis, testosterone production), ducts, glands, penis.
- Female: ovaries (folliculogenesis, oogenesis, hormone production), uterine tubes, uterus (menstrual cycle), cervix, vagina, mammary glands.
- Cyclical changes regulated by pituitary and ovarian hormones.
Special Senses
- Eye: cornea, lens, retina (rods/cones), support structures; phototransduction.
- Ear: external, middle, inner regions; cochlea (hearing), vestibular apparatus (balance).
Key Terms & Definitions
- Histology — the study of tissues at the microscopic level.
- Fixation — process to preserve tissue structure for microscopy.
- Epithelial Tissue — tissue covering surfaces, lining cavities, and forming glands.
- Connective Tissue — tissue providing structural and metabolic support.
- Muscle Tissue — tissue specialized for contraction and movement.
- Nervous Tissue — tissue specialized for electrical impulse conduction.
- Osteon — structural unit of compact bone; Haversian system.
- Gland — tissue or organ that secretes substances for use in the body or for elimination.
Action Items / Next Steps
- Review supplemental micrographs online at www.thePoint.com/Eroschenko12e for histological images.
- Practice identifying tissue types and organ structures in microscope or digital images.
- Study chapter summaries for each system for exam preparation.
- Complete any provided online quizzes or checklists for self-assessment.