Diversity of Cells and Their Function

Haematoxylin and eosin

• Haematoxylin stains acidic molecules purple

• Eosin stains basic molecules pink

Epithelium

• Cover surfaces of the body, lines hollow organs, forms glands

• Backed by a basal lamina (basement membrane) - thin layer of specialised extracellular material between the basal surface of epithelial cells and the underlying tissue

• Non-vascular

• Cells usually polarised - apical and basal sides differ
• Apical: faces the lumen of a tube or the external environment
• Basal: attaches to the basement membrane

Functions

• Mechanical barrier

• Chemical barrier

• Absorption

• Secretion

• Containment

• Locomotion

Classification

• Squamous: flattened

• Cuboidal: cube

• Columnar: tall and thin

• Simple: one layer

• Stratified: 2+ layers

• Pseudostratified: multiple layers, all in contact with basal lamina

• Microvilli

• Cilia

• Keratinized

• e.g. goblet cells

Glandular epithelia

• Endocrine: product secreted towards basal end of cell and distributed by vascular system - ductless

• Exocrine: product secreted towards apical end of cell - ducted

Connective tissue

Soft connective tissue

• Tendons, ligaments

• Loose: loosely packed fibres separated by ground substance

• Dense: densely packed bundles of collagen fibres
• Dense regular: fibres aligned
• Dense irregular: fibre bundles run in many directions

Hard connective tissue

• Strong, flexible, compressible, semi-rigid tissue

• 3 types of cartilage - hyaline, elastic, fibrocartilage

• Bone
• Outer shell of cortical bone makes up shaft - diaphysis
• Cancellous/trabecular bone occupies ends - epiphyses

Blood and lymph

• Fluid connective tissues

Muscle

• Specialized to generate force by contraction

• Force is movement of actin fibres over myosin fibres

• Smooth muscle: involuntary, non-striated

• Skeletal muscle: voluntary, striated, multinucleated

• Cardiac: involuntary, striated, single nucleus at centre of fibre
• Has intercalated discs - contain many intracellular junctions for stability

Nervous tissue

• Consists of neurons and their supporting cells (glia)

• Control function and allow for rapid communication between different parts of the body

• Surrounded by connective tissue coat
• Meninges in CNS
• Epineurium in PNS

Glia of the CNS

• Astrocytes: provide support, involved in ion transport

• Oligodendrocytes: produce myelin

• Microglia: immune surveillance

Glia of the PNS

• Schwann cells: produce myelin and support axons