Histologie 2: Cellules et Tissus

Study Notes

Cellule: Basic structural and functional unit of living organisms
- In the human body: ~100 trillion cells, ~200 different cell types
- Average size: ~200 µm
Tissues: Four primary types
- Epithelial: Covering and secretion functions
- Connective: Supporting, protection and connection functions
- Muscular: Movement
- Nervous: Regulation and communication functions
Tissue Levels: Cells with similar morphology and function grouped together
Observation Techniques:
- Macroscopic: Visible to the naked eye (human, chicken)
- Microscopic: Viewed using a microscope (light microscope, colored dyes)
Cellular Structure:
- Cytoplasm: Internal fluid of the cell
- Extracellular matrix: Material outside the cell membrane
- Cell membrane: Surrounds the cell
- Nucleus: Contains cell's genetic material
- Intracellular fluid: Material inside the cell membrane
- Cell junctions: Connections between cells
Tissue: Assemblage of cells working together, with unique functions
- Organs: Composed of different tissues with specific tasks
- Types of tissues: Epithelial (covering), Connective, Muscular, Nervous(specialized in regulation, communication)

Endocrine Glands: Secrete hormones directly into the bloodstream, acting at a distance
- Structure: Clusters or cords of cells
Exocrine Glands: Secrete substances through ducts, leading to a specific location
- Structure: Various shapes and structures
Amphicrine Glands: Dual function, possessing both endocrine and exocrine properties (e.g., pancreas)

Organization Levels (Human Body):
- Chemical (atoms, molecules)
- Cellular (organelles, cells)
- Tissue (epithelial, connective, muscular, nervous)
- Organ (specific structures)
- Organ system (groups of organs)
- Organism (human body)
Atoms in Living Things:
- Primarily: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S)
- Also: Calcium (Ca), Sodium (Na), to Potassium (K), Chlorine (Cl), Magnesium (Mg), Iron (Fe), amongst others.
Examples of Organelles
- Mitochondria
- Endoplasmic Reticulum
- Ribosomes
- Lysosomes & Peroxisomes
- Plasma Membrane

Epithelium: Cells tightly packed together, often with a basement membrane
- Types: Simple squamous, stratified squamous, cuboidal, columnar, transitional
- Functions: Covering, lining, absorption, secretion
Specialized Epithelial Features
- Basement Membrane (structural support)
- Cell shapes (cuboidal, columnar, squamous for specialized function)
- Cell layers (single or multiple for increased protection/diffusion or barrier)
Epithelium Stratifications:
- Simple: Single layer
- Pseudostratified: Appears layered but cells rest on the basement membrane
- Stratified: Multiple layers
Types of Epithelial cells: squamous, cuboidal and columnar.

Glandular Epithelium:
- Secretion (hormones or other substances)
- Exocrine glands (discharge substances via ducts onto a surface)
- Endocrine glands (release hormones directly into the bloodstream)
- Classification based on secretion type (serous, mucous, etc.) and structure (tubular, acinar).

Connective Tissues: Support and connect other tissues and organs
- Types: Loose, dense, cartilage, bone, blood
- Components include cells embedded in a matrix of ground substance and fibers (collagen, elastic, reticular).
Types of Connective Tissue:
- Specialized
- Non-specialized

Bone Tissue: Main component of the skeleton, providing support and protection
Types of Bone: Compact (dense) and spongy (cancellous)
Bone Cells: Osteoblasts (forming bone), osteocytes (maintain bone), osteoclasts (resorbing bone)
Bone Development: Intramembranous (from fibrous membrane) and endochondral [cartilage] (from hyaline cartilage) ossification processes

Connective tissue: Provides support and connection between different tissues.
- Characterised by cells embedded within an extracellular matrix.
- Types: Connective tissue proper (loose and dense), cartilage, bone, blood.
- Roles: Support, protection, connection, transportation.
Non-specialized cells: Mesenchymal cells (stem cells), Fibroblasts(synthesizing extracellular matrix).
- Specialized cells: Chondrocytes(cartilage), Osteocytes(bone), etc.
- Extracellular matrix: Composed of ground substance and various types of fibers (collagen, elastic).

Nervous Tissue: Composed of neurons (transmitting electrical impulses) and glial cells (supporting and nourishing the neurons).
- Functions: Communication, coordination, control, and perception
Neural Tissue Structure: Neurons, with axons and dendrites; neuroglia
Nervous System Divisions: Central nervous system (brain and spinal cord), peripheral nervous system (nerves and ganglia)
Importance of Imaging Techniques in diagnosing nervous system diseases/tumours and/or trauma.