1. VAN-504, Lecture - 02
Epithelia and their modifications. Connective tissue and its components including blood and bone

2. Tissues
Definition: a group of closely associated cells that perform related functions and are similar in structure.
Four basic types of tissue function
Epithelium covering
Connective tissue support
Muscle tissue movement
Nervous tissue control

3. Epithelial Tissues General Characteristics
1.Epithelial tissue is widespread throughout the body, covers
organs, and lines body surfaces.
2.Epithelial tissues -
- are anchored to a basement membrane
- are made up of tightly packed cells
- contain little intercellular material
- generally lack blood vessels, Avascular but innervated
- are replaced frequently, regeneration
3.Polarity
- Free upper (apical) surface
- Lower (basal) surface contributing basal lamina to basement membrane

4. Epithelia (plural)
Epithelium: sheet of cells that covers a body surface or lines a body cavity; also form most of the body’s glands
Functions:
Protection
Absorption
Sensory reception
Secretion
Filtration
Formation of slippery surfaces for movement

5. Epithelial tissues function in
Epithelial tissues function in protection, secretion, absorption, excretion, and sensory reception.

7. Epithelium
Have one free (unattached) surface or edge called the apical surface
Exposed to body’s exterior or to the cavity of an internal organ
Lower surface of an epithelium rests on a basement membrane
Structureless material secreted by both the epithelial cells and the connective tissue cells

8. Classification of Epithelia
According to thickness
“simple” - one cell layer
“stratified” – more than one layer of cells (which are named according to the shape of the cells in the apical layer)
According to shape
“squamous” – wider than tall
“cuboidal” – as tall as wide
“columnar” - taller than wide

9. Classification of Epithelium
According to relative number of cell layers
Simple (one layer of cells)
Stratified (more than one cell layer)

10. Classification of Epithelium
According to the shape of cells
Squamous (cells flattened like scales)
Cuboidal (cube-shaped)
Columnar (shaped like columns)

11. Simple Squamous Epithelium
Simple squamous (SS) tissue is composed of flat, scale-like cells that usually forms membranes.
Single row of flat cells
It lines the walls of blood vessels, pulmonary alveoli (Shown in slide), and the lining of the heart, lung, peritoneal cavities glomeruli, endothelium, and serosa
Permits diffusion of substances
Secretes serous fluid

12. Simple Squamous Epithelium

13. Simple Cuboidal Epithelium
This tissue is composed of a single layer of cube-like cells with microvilli.
Absorption and secretion, mucus production
It lines the walls of kidney tubules, covers the
surface of ovaries, and is common in glands
and their ducts, Liver, thyroid, mammary and
salivary glands, bronchioles, and kidney tubules

14. Simple Cuboidal Epithelium

15. Simple Cuboidal Epithelium

16. Simple Columnar Epithelium
This tissue is composed of a single layer of tall
narrow cells.
- oval nuclei in basal half of cell
It often includes mucus-producing goblet cells.
It often lines the digestive tract, uterus, kidney and uterine tubes
Absorption and secretion; mucus secretion.

17. Simple Columnar Epithelium

18. Simple Columnar Epithelium

19. Pseudo stratified Epithelium
Secretes and propels respiratory mucus
Although this tissue appears stratified, it is actually composed of a single layer of cells of different types. some not reaching free surface.
Although their nuclei are found at different levels, It give layer stratified look.
Each cell adjoins the basal membrane (BM).
This tissue lines the larger respiratory passageways.
It is often ciliated.

20. Pseudo stratified Epithelium

21. Pseudo stratified Columnar Epithelium
Main functions: absorption and secretion
Ciliated variety lines respiratory tract
Mucus produced by goblet cells traps dust and other debris
Cilia propel mucus upward and away from the lungs

22. Stratified Epithelia More than one layer of cells
Named for shape of surface cells
exception is transitional epithelium
Deepest cells on basement membrane
Variations
keratinized epithelium has surface layer of dead cells
Non keratinized epithelium lacks the layer of dead cells

23. Stratified: regenerate from below

24. Keratinized Stratified Squamous
Multilayered epithelium covered with dead squamous cells, packed with keratin
epidermal layer of skin

25. Nonkeratinized Stratified Squamous
Multilayered surface epithelium forming moist, slippery layer
Tongue, oral mucosa, esophagus and vagina

26. Stratified Cuboidal Epithelium
Two or more cell layers; surface cells square
Secretes sweat; produces sperm and
hormones
Sweat gland ducts; ovarian follicles and
seminiferous tubules
Stratified cuboidal epithelium (SC) is found in the ducts of sweat glands and surrounds Graafian follicles of ovaries (shown below

27. Stratified Cuboidal Epithelium

28. Transitional Epithelium
Multilayered epithelium surface cells that change from round to flat when stretched
allows for filling of urinary tract
ureter and bladder
Shape of cells depends upon the amount of stretching
It lines organs of the urinary system.

29. Transitional Epithelium

30. Ciliated Epithelium
Some epithelial membranes are made up of cells with cilia, tiny projections that beat in unison to move mucus along the surface.
Ciliated epithelia in the trachea, for example, sweep debris out of the respiratory tract.

31. Glandular Epithelium
A gland is defined as one or more cells responsible for secreting a particular product
Two major gland types
Endocrine gland
Ductless since secretions diffuse into blood vessels
All secretions are hormones
Examples include pituitary, pancreas, ovaries, testes
Exocrine gland
Secretions empty through ducts to the epithelial surface
Include sweat and oil glands

32. Endocrine and Exocrine Glands
Secrete substances
composed of epithelial tissue
Exocrine glands connect to surface with a duct (epithelial tube)
Endocrine glands secrete (hormones) directly into bloodstream
Mixed organs do both
liver, gonads, pancreas
Unicellular glands – endo or exocrine
goblet or intrinsic cells of stomach wall

33. Connective Tissue Connective tissue
Connective tissue proper (examples: fat tissue, fibrous tissue of
ligaments)
Cartilage
Bone
Blood
Widely spaced cells separated by fibers and ground substance
Most abundant and variable tissue type
Functions
connects organs
gives support and protection (physical and immune)
stores energy and produces heat
movement and transport of materials

34. Cells of Connective Tissue
Fibroblasts produce fibers and ground substance
Macrophages phagocytize foreign material and activate immune system
arise from monocytes (WBCs)
Neutrophils wander in search of bacteria
Plasma cells synthesize antibodies
arise from WBCs
Mast cells secrete
heparin inhibits clotting
histamine that dilates blood vessels
Adipocytes store triglycerides

35. Fibers of Connective Tissue
Collagen fibers (white fibers)
tough, stretch resistant, yet flexible
tendons, ligaments and deep layer of the skin
Reticular fibers
thin, collagen fibers coated with glycoprotein
framework in spleen and lymph nodes
Elastic fibers (yellow fibers)
thin branching fibers of elastin protein
stretch and recoil like rubberband (elasticity)
skin, lungs and arteries stretch and recoil

36. Connective Tissue Ground Substance
Gelatinous material between cells
absorbs compressive forces
Consists of 3 classes of large molecules
glycosaminoglycans – chondroitin sulfate
disaccharides that attract sodium and hold water
role in regulating water and electrolyte balance
Proteoglycan (bottlebrush-shaped molecule)
create bonds with cells or extracellular macromolecules
adhesive glycoproteins
protein-carbohydrate complexes bind cell membrane to collagen outside the cells

37. Classes of Connective Tissue

38. Fibrous Connective Tissue Types
Loose connective tissue
gel-like ground substance between cells
types
areolar
reticular
adipose
Dense connective tissue
fibers fill spaces between cells
types vary in fiber orientation
dense regular connective tissue
dense irregular connective tissue

39. Areolar Tissue
Loose arrangement of fibers and cells in abundant ground substance
Underlies all epithelia, between muscles, passageways for nerves and blood vessels

40. Areolar Tissue

41. Reticular Tissue Loose network of reticular fibers and cells
Forms supportive stroma (framework) for lymphatic organs
Found in lymph nodes, spleen, thymus and bone marrow

42. Reticular Tissue

43. Adipose Tissue
Empty-looking cells with thin margins; nucleus pressed against cell membrane
Energy storage, insulation, cushioning
subcutaneous fat and organ packing
brown fat (hibernating animals) produces heat

44. Adipose Tissue

45. Dense Regular Connective Tissue
Densely, packed, parallel collagen fibers
compressed fibroblast nuclei
Tendons and ligaments hold bones together and attach muscles to bones

46. Dense regular Connective Tissue

47. Dense Irregular Connective Tissue
Densely packed, randomly arranged, collagen fibers and few visible cells
withstands stresses applied in different directions
deeper layer of skin; capsules around organs

48. Dense Irregular Connective Tissue

49. Cartilage Supportive connective tissue with rubbery matrix
Chondroblasts produce matrix
called chondrocytes once surrounded
No blood vessels
diffusion brings nutrients and removes wastes
heals slowly
Types of cartilage vary with fiber types
hyaline, fibrocartilage and elastic cartilage

50. Hyaline Cartilage
Rubbery matrix; dispersed collagen fibers; clustered chondrocytes in lacunae
supports airway, eases joint movements
Ends of bones at movable joints; sternal ends of ribs; supportive material in larynx, trachea, bronchi and fetal skeleton

51. Hyaline Cartilage

52. Elastic Cartilage Hyaline cartilage with elastic fibers
Provides flexible, elastic support
external ear and epiglottis

53. Elastic Cartilage

54. Fibrocartilage
Hyaline cartilage with extensive collagen fibers (never has perichondrium)
Resists compression and absorbs shock
pubic symphysis, meniscus and intervertebral discs

55. Fibrocartilage

56. Bone Spongy bone - spongy in appearance
delicate struts of bone
covered by compact bone
found in heads of long bones
Compact bone - solid in appearance
more complex arrangement
cells and matrix surround vertically oriented blood vessels in long bones

57. Bone Tissue (compact bone)
Calcified matrix in lamellae around central canal
Osteocytes in lacunae between lamellae
Skeletal support; leverage for muscles; mineral storage

58. Bone

59. Blood
Variety of cells and cell fragments; some with nuclei and some without
Nonnucleated pale pink cells or nucleated white blood cells
Found in heart and blood vessels

60. Blood

62. Mast Cell

63. Lymphocytes

66. Microphages

67. Nervous Tissue Nervous tissue Neurons Supporting cells
Large cells with long cell processes
surrounded by smaller glial cells lacking processes
Internal communication between cells
in brain, spinal cord, nerves and ganglia

68. Nervous Tissue

69. Muscle Tissue Elongated cells stimulated to contract
Exert physical force on other tissues
move limbs
push blood through a vessel
expel urine
Source of body heat
3 histological types of muscle
skeletal,
cardiac and
smooth

70. Skeletal Muscle
Long, cylindrical, unbranched cells with striations and multiple peripheral nuclei
movement, facial expression, posture, breathing, speech, swallowing and excretion

71. Skeletal Muscle

72. Cardiac Muscle
Short branched cells with striations and intercalated discs
one central nuclei per cell
Pumping of blood by cardiac (heart) muscle

73. Cardiac Muscle

74. Smooth Muscle
Short fusiform cells; nonstriated with only one central nucleus
sheets of muscle in viscera; iris; hair follicles and sphincters
swallowing, GI tract functions, labor contractions, control of airflow, erection of hairs and control of pupil

75. Smooth Muscle