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USLS COLLEGE OF MEDICINE
HISTOLOGY
TITLE: Histology Course Introduction
(Cell Epithelia & Glabds)
DATE: August 27, 2020
LECTURER: Dr. David Pedroza, MD,
DPSP
REFERENCE: Wheater’s 5th^ ed, Doc
Pedroza’s ppt
OUTLINE
I. Histology II. Cell A. Cell nucleus & Cytoplasm B. Membrane Structure C. Cell Structure Cell nucleus Cytoplasm Nucleolus Nuclear Envelope Rough ER Smooth ER III. Biochemical Functions of the body A. Import, Export & Intracellular Transportation Passive Diffusion Facilitated Diffusion Active Diffusion Bulk Transport B. Cytoskeleton & Cell Movement Microfilaments Intermediate Filaments Microtubules IV. Epithelial Tissue A. Epithelial Cells Simple Squamous Cuboidal Columnar Stratified Squamous Transitional Pseudostratified B. Apical Specializations Microvilli Cilia Dynein C. Intermediate Filaments Desmosome Hemidesmosome Zonula adherens Macula adherens Zonula Occludens Nexus (Gap junction)
Course Objectives:
- Understand basic cell structure and correlate with corresponding function.
- Describe the different epithelia and their orientation to more complex organization and describe the cytoskeletal organization
I. HISTOLOGY
- Microscopic study of tissues and organs
- Microscopic anatomy and histochemistry
- Provides understanding to structure and function of normal mammalian (mainly human) tissue HISTOPATHOLOGY – known as the study of changes
- Sound knowledge of normal structure is essential for an understanding of pathology
II. CELL What is a cell?
- Functional unit of all living organisms
- Single cell – simplest organisms such as bacteria and algae
- complex organisms (many cells + matrix)
- Evolution allows specialization (structures and functions) of many cells ( differentiation)
- Makes alive things (organisms) Prokaryotes (mainly bacteria) have some major structural differences Human (and all other eukaryotic) cells consist of a nucleus and cytoplasm. The cytoplasm contains a number of organelles each with a defined function. The nucleus may be considered the largest organelle A. Cell Nucleus and Cytoplasm
B. Membrane Structure
B. Cell Structure
(a) Cell Nucleus
(a) Cytoplasm (b) Nucleolus
(c) Nuclear envelope
(d) Rough ER
(e) Smooth ER
III. BIOCHEMICAL FUNCTIONS OF THE BODY
- Import, export and intracellular transportation
- Energy production and storage
- Lipid biosynthesis
- The cytoskeleton and cell movement
- The integrated function of cells in tissues, organs and organ systems
IV. EPITHELIAL TISSUE
An epithelium is a cohesive sheet of cells that:
- Covers the external surfaces and lines of the internal surfaces of the body
- Barrier o Protection (by withstand wear and tear from hydration and dehydration) o Selective absorption – control the movement of substances between the outside environment and the internal compartments, or between compartments in the body
- Transport (ions, O2, CO2)
- Secretion (secretory cells)
- Forms endocrine and exocrine secretory glands.
Abdomen – abdominal wall and intestines
- Skin a. Epidermis – Epithelium (Stratified) b. Dermis – connective tissue
- Superficial Fascia a. Hypodermis – Fatty Connective Tissue
- Deep Fascia a. Epimysium – Connective Tissue
- Intestinal Mucosa a. Epithelium (Simple) b. Connective Tissue
Epithelial lining cells of:
- Skin – multiple layers of cells
- Intestines – single layer of tall (columnar) cells
A. Epithelial Cells
- Capable of renewal and regeneration a) Non – specialized epithelium – all cells b) Specialized epithelium – stem cells
- Are structurally and functionally polarized: have apical, lateral and basal domains
- Are held together by several basolateral specialization, known as the intercellular junctions, and bind to the underlying connective tissue via the basement membrane (LM) or basal lamina (EM)
A) Simple a) Squamous- endothelium and mesothelium (non – specialized: renewal via mitosis)
b) Cuboidal – kidney tubules (non – specialized: renewal via mitosis)
c) Columnar – gut mucosa (specialized: renewal via stem cells); lining the gut lumen
B) Stratified a) Squamous
- Non – Keratinized – line esophagus, oral, vagina
- Keratinized – line thick and thin skin
b) Transitional – urothelium; lines the urinary tract, ureter, bladder and urethra
- cells on the surface are often dome (umbrella) shaped and some cells reveal two nuclei.
c) Pseudostratified Columnar (Respiratory)
**B. Apical Cell Surfaces Specializations
- MICROVILLI**
- aka “brush border” or “striated border”
- Core of actin filaments
- Non – motile; serve to increase surface area
SUMMARY:
EPITHELIUM
Types – simple & stratified (pseudostratified)
Apical cell surface specialization
o Microvilli – actin filaments o Cilia – microtubules (dynein)
Intercellular junctions o Zonula occludens (tight junction) – ridges and grooves, seal intercellular spaces – selective permeability barrier o Zonula adherens – actin filaments – cell to cell adhesion o Macula adherens (desmosome) – intermediate filaments attachment plaque (spot) o Hemidesmosome – attaches epithelium to basal lamina o Nexus (gap junction) – connexons – cell to cell communication
Epithelial cells form Secretory Glands
Glands: grouping of cells specialized for secretion
Secretion – the process by which small molecules are taken up and transformed, by intracellular biosynthesis, into a more complex product that is then actively released from the cell.
Exocrine (ducts) and Endocrine (ductless) glands
