1. General Histology Histos+logus= Histology (Science of tissues).
- A cell is the basic unit of an organism.
- A group of cells whether similar or different cells) may form a tissue.
- A group of tissues may form an organ.
A group of organs will establish a living organism (multicellular animals).
Tissue: is groups of cells closely associated that have a similar structure and perform a related function
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

2. Classification of cells
Prokaryotic cell (prokaryote)
A unicellular organism that lacks a membrane-bound nucleus (karyon), mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek (pro) "before" and κάρυον (karyon) "nut or kernel”.
2 domains, archaea and bacteria
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI)
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

3. Eukaryotic Amoeba, Muscle cell
In contrast, species with nuclei and organelles are placed in the domain Eukaryota.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

4. Comparison of eukaryotes vs. prokaryotes
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

5. Cell division
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

6. Cell division
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

7. Tissue culture
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

8. Key Terms Histology: the study of tissues. Tissues:
Simply groups of similar cells that work together performing the same task
Greatest form of teamwork in the body

9. Why Study Histology?
Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.

10. Tissues Four types of tissue Epithelial = covering
Connective = support
Muscle = movement
Nervous = control
Most organs contain all 4 types
Connective tissue has non-living extra-cellular material [ECM] or (matrix) between its cells
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

11. 4 Types of Tissue . Epithelium . Connective . Muscle . Nervous
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

12. * made of all four tissue types
Skin, our largest organ
* made of all four tissue types

13. Epithelial Tissue Makes up 3% of your body weight They don’t move
They don’t send messages
Their cells are all touching one another
Of all tissues, they are the most widely varied in structure and function.
All sit on a basement membrane.

14. Epithelial Tissues Sheets of cells
Specialized contacts/cell junctions (see below)
Basal lamina: protein scaffolding secreted by epithelial cells
Basement membrane: reticular fibers (crossed collagen network) that supports epithelium--really associated connective tissue
Connective tissue support
Nutrients from capillaries in underlying connective tissue
Nerves pass through
Easily regenerates
E.g. skin, lining of gut, mucous membranes
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

15. Locations of Epithelial Tissues
Covers the body (epidermis)
Found on the inside of hollow organs and the outside of all organs
Found above a connective tissue layer (epi = above)
Lines the cavities, tubes, ducts, and blood vessels inside the body.

16. Epithelial Anatomy
Apical surface – upper surface, is free or exposed to the “exterior”
Basal surface – attached surface (below)
Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done

17. Functions of Epithelial Tissue
Protects from physical & chemical injury
Protects against microbial infection
Contains nerve endings which respond to stimuli.
Filters, secretes & reabsorbs materials
Secretes fluids to lubricate joints

18. Cell Organization
Simple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is needed
simple squamous
simple cuboidal
simple columnar
Stratified – layers of cells; common in areas where protection is needed like the skin
stratified squamous
stratified cuboidal
stratified columnar

19. Classes of Epithelia Simple: just one layer or cell shape
Stratified: multiple layers and cell shapes
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

20. Epithelial Tissue in Review…

21. Three Basic Shapes Squamous – like scales,
or pancakes (“being squashed like a pancake”)
Cuboidal – looks like cubes
Columnar – longer and look like columns

22. Two Types of Stratified Columnar
Ciliated
Unciliated
cilia
No cilia

23. Squamous Epithelium Simple – one cell thick
Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities
Stratified – multiple layers
Forms epidermis

24. Cuboidal Epithelium Cuboid Cells Simple – one cell thick
Roughly cube shaped
Duct
Line ducts in kidneys where re-absorption and secretion activities take place.
Cuboid Cells
Duct

25. Columnar Epithelium Simple – one cell thick
Column shaped (long and narrow)
Lines digestive tract where re-absorption & secretion occurs.

26. Confusing Epithelial Tissue
Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it is squamous or cuboidal
Shape of cells depends upon the amount of stretching (urinary bladder)

27. Confusing Epithelial Tissue Continued…
“Pseudostratified Columnar Epithelium”
Looks like it has more than one layer because of the position of the nucleus
Nuclei are positioned at differing levels
Cells narrow in the area without nucleus

28. Types of Epithelial Membranes
Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina)
Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs)
Cutaneous or skin – body surface; protection
Synovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)

29. Stratified Epithelia Squamous Transitional epithelium E.g. epidermis
E.g. urinary structures--bladder
Stretches from 6 cells to 3 cells thick as bladder fills and expands
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

30. Quiz!! Can You Identify the Classes of Epithelium? E D A B C
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

31. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

32. 1). limit the passage of molecules;
Tight junctions: impermeable e.g. gut tube, doesn’t let enzymes from gut into blood stream.
Tight junctions seal adjacent epithelial cells in a narrow band just beneath their apical surface. They consist of a network of claudins and other proteins. T.J. perform two vital functions:
1). limit the passage of molecules;
2). ions through the space between cells.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

33. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

34. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

35. Cell Junctions
Desmosome: binding spots between cells with proteins called cadherins
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

36. Desmosomes
 Are intercellular junctions that provide strong adhesion between cells.
Also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

37. Are tubes that let small molecules pass between cells.
Gap junctions
Are tubes that let small molecules pass between cells.
Are a specialized intercellular connection between a multitude of animal cell-types.
Directly connect the cytoplasm of adjacent cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

38. Features of Lateral Surface of Epithelium
Cells are connected to neighboring cells via:
Proteins-link cells together, interdigitate
Contour of cells-wavy contour fits together
Cell Junctions
Desmosomes-adhesive spots on lateral sides
Tight Junctions-at apical area, plasma membrane of adjacent cells fuse, nothing passes
Gap junction-spot-like junction occurring anywhere, lets small molecules pass
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

39. Features of Apical Surface of Epithelium
Microvilli: In small intestine
Finger-like extensions of the plasma membrane of apical epithelial cell
Increase surface area for absorption
Cilia: Respiratory tubes
Whip-like, motile extensions
Moves mucus, etc. over epithelial surface 1-way
Flagella: spermatoza
Extra long cilia
Moves cell
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

40. Features of the Basal Surface of Epithelium
Basal lamina: supportive sheet between epithelium and underlying connective tissue
Selective filter
Basement membrane = basal lamina plus underlying reticular fiber layer
Attaches epithelium to connective tissue below
Sometimes the two are used interchangeably
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

41. Name that Epithelial Feature! (name and location on cell)3
Cilia
Tight junction
Microvilli
Basement membrane 3 1 1 2 2 4 4
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

42. Glands: epithelial cells that make and secrete a water-based substance
Exocrine Glands
Secrete substance onto body surface or into body cavity
Have ducts
E.G., salivary, mammary, pancreas, liver
Endocrine Glands
Secrete product into blood stream
Either stored in secretory cells or in follicle surrounded by secretory cells
Hormones travel to target organ to increase response
No ducts
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

43. GLANDS
A cell or an organ in human and animals that synthesizes chemical substances and secretes them for the body to use or eliminate, either through a duct (exocrine gland) or directly into the bloodstream (endocrine gland)
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).