1. Tissues -four primary tissue types: 1. Epithelial 2. Connective
3. Muscle
4. Neural
-however: all tissues in the body develop from three germ layers
1. ectoderm - epithelial + neural
2. mesoderm - connective + muscle + some epithelial
3. endoderm – organs + some epithelial

2. Epithelial Tissue = lining epithelium & glands
lining epithelium = line body surfaces and cavities
glandular epithelium = secretion
multiple functions of epithelial tissue:
1. protection (chemical and physical) – e.g. from dehydration, pathogens
2. synthesis – e.g. hormones, vitamins
3. regulation - e.g. body temperature, transport via permeability
4. excretion - e.g. wastes
5. absorption – e.g. nutrients
6. immune response
7. detection – detection of extracellular signals

3. Cellularity Polarity Attachment to each other to connective tissue
Epithelial characteristics
Cellularity
Polarity
Attachment
to each other
to connective tissue
Avascularity
Regeneration

4. Epithelial tissue characteristics
1. Cellularity: epithelial tissues are composed almost entirely of cells held together by cell junctions
-very little to no extracellular matrix
2. Polarity: epithelial cells possesses an exposed surface that faces the exterior
or into the lumen of an organ - apical face
-also has an attached base which is anchored to other tissues (usually a
connective tissue - basal face
-the organelles are not uniformly
distributed in epithelial cells

5. Epithelial characteristics Epithelial characteristics
3. Attachment: in many animals, epithelial tissues are attached to underlying tissues via the basement membrane
-BM is produced by the basal surface of the cells & connective tissue - comprised of
collagen type IV and laminin
-the BM is comprised of two layers:
a. closest to epithelial cell = basal lamina
(glycoproteins, laminin and actin)
-acts as a barrier to transport from underlying
tissue into the epithelium
b. furthest from the epithelial
cell = reticular lamina
-collagen IV bundles produced by the underlying connective tissue cells
-provides a strong connection to the
connective tissue

6. Epithelial characteristics Epithelial characteristics
1. Tight junctions: lipid portions of plasma membranes are bound together by interlocking membrane proteins forming a complex just underneath the apical face
-very tight union - prevents passage of water and solutes between the two cells
3. Attachment: also form extensive connections between each other

7. Epithelial characteristics Epithelial characteristics
2. Gap junctions: two cells held together by protein called connexons
-connexons grouped together as hexamers
-act as channels linking adjacent cells
-materials can freely move between
the two cells when the connexons open
-passage of materials helps to coordinate the activities of the two cells
e. g beating rhythm of cilia

8. 3. Desmosomes: comprised of
a protein plaque that links to the cytoskeleton of the cell (via keratin)
-made up of a protein called desmoplakin
cellular adhesion molecules/CAMs known as cadherins (desmoglein and desmocollin)
-the CAMs link protein “plaques” from adjacent cells to one another
-require calcium to work
-several types of desmosomes known: belt, hemi, button
-hemidesmosome: attaches the cell to the basement membrane of the tissue
-link to a basement membrane protein = laminin

9. Epithelial characteristics
4. Avascularity: do not contain blood vessels
-must obtain nutrients via diffusion or absorption
5. Regeneration: damaged cells are replaced through differentiation of
stem cells located deep within the tissue
-rate of renewal depends on rate of cell death
-stem cells = germinative cells
-these cells are found closest to the basement membrane
-migrate towards the surface and differentiate

10. Classification of Epithelia
catagorizing epithelial tissue types
A. # of layers
simple = 1 layer
stratified = multiple
**pseudo = 1 layer
B. Cell shape
columnar
cuboidal
squamous

11. Simple Epithelium
-relatively thin
-cells have the same polarity - nuclei are generally aligned
-very fragile - cannot provide mechanical/physical protection
-line internal compartments
-relatively permeable - absorptive surfaces, secretion, filtration
Stratified Epithelium
-thicker due to multiple layers
-found in areas subject to mechanical and chemical stress
e.g. skin, mouth
-tougher than simple epithelia
-organelles do not align

12. Pseudostratified Epithelium
-appears to be stratified
-yet the basal surface of every cell contacts basement membrane
-apical surface of some cells possess cilia
-other cells within the epithelium secrete mucus – goblet cells
-found lining absorptive organs
e.g. respiratory epithelium

13. Squamous Epithelium
-tile-like cells - cells are thin, flat and irregular in shape
-cells interlock like tiles
-very difficult to see from the side due to their thinness
-simple squamous - most delicate tissue in the body
-found in protected regions where absorption occurs
-many types: mesothelium - lines ventral body cavity
(i.e. abdomen)
endothelium - lines heart and vessels

14. SIMPLE SQUAMOUS

15. Squamous Epithelium
-stratified squamous – found where mechanical stresses are severe
e.g. epidermis of the skin
e.g. lining of the oral cavity, anal canal
-cells on exposed surfaces may contain keratin - an intermediate filament protein that reduces water loss and
provides strength = keratinized epithelium
-non-keratinized epithelium is tough but must be kept moist

16. STRATIFIED SQUAMOUS - KERATINIZED

17. STRATIFIED SQUAMOUS - KERATINIZED

18. Transitional Epithelium
-a stratified squamous epithelium that permits stretching
-located in walls of the bladder, renal pelvis and the ureters
e.g. bladder wall - when empty the epithelium looks as if it has several layers
-actual number of layers can be seen upon distension

19. TRANSITIONAL

20. Cuboidal Epithelium -cells are cubes
-nucleus is large, round and in the center of the cell
-simple cuboidal: regions of secretion, absorption and excretion
e.g. kidney tubules – absorption of salts and water, excretion of wastes
e.g. pancreas & salivary glands - buffers & enzymes
e.g. thyroid follicles - thyroid hormones

21. SIMPLE CUBOIDAL

22. SIMPLE CUBOIDAL

23. Cuboidal Epithelium -stratified cuboidal: relatively rare
-ducts of sweat glands and mammary glands

24. Columnar Epithelium -height is greater than their width
-nuclei is close to the BM and can be more oval shape
-simple columnar: provides some protection but is mainly for absorption and secretion
-often possess microvilli at their exposed apical faces
e.g. lining of the small intestines – i.e. absorptive cells

25. Simple columnar epithelium
microvilli
wandering lymphocytes
-usually involved in secretion and absorption
-located in the gallbladder, larger ducts of exocrine glands, gastric pits of stomach
-basally located nuclei aligned with one another
-frequently the apical face is modified with cellular extensions
e.g. microvilli – intestinal lining = brush border
-short-lived cells – replaced every 4 to 5 days
-frequently found with Goblet cells (intestine and stomach)

26. Columnar Epithelium -stratified columnar: relatively rare
-two to multiple layers
-only outer layer contains truly columnar cells
-protection role

27. Stratified columnar epithelium

28. Columnar Epithelium
-pseudostratified columnar: only a single layer because the basal
face of every cell contacts the basement membrane
-nuclei are at varying levels - appearance of multiple layers
-exposed apical surface typically bears cilia
e.g. respiratory epithelium

29. Pseudostratified
-these tissues are generally ciliated

30. Connective Tissue binds structures together
e.g. dense and elastic connective tissues
provides support
e.g. bone, reticular tissue
fills cavities
e.g. adipose tissue, loose areolar tissue
produces blood
e.g. bone marrow
protects organs & structures
bone and cartilage

31. Connective Tissue components: matrix + cells
-matrix: non-cellular support material
-comprised of extracellular protein fibers
e.g. 1. collagen fibers (white) – type I
2. elastic fibers (yellow)
3. reticular fibers – collagen type III
4. fibronectin
-plus a ground substance = water + sugars, proteoglycans and glycoproteins
-cells: secrete the matrix
-most basic kind of connective tissue cell = fibroblast
-some have become very specialized and make a very specialized matrix
e.g. osteoblasts of bone

32. Connective Tissues -cell types possible in connective tissue:
fibroblasts: immature cell type found in basic connective tissues like areolar
tissue, reticular tissue, dense connective tissues
-secrete the extracellular matrix
-secrete main component of matrix = collagens
-also produce hyaluronan = glycosaminoglycan (sugar) that gives the
ground substance a viscous quality
-also produce the other components of the ground substance
e.g. proteoglycans
adipocytes: main cellular component of adipose tissue
-more specialized type of fibroblast – fat storage
-fill with lipid upon maturation
-found in adipose tissue and areolar tissue
C. melanocytes: synthesize and secrete melanin
-dark, brown pigment that absorb light
-found in areolar tissue

33. Connective Tissues
D. Macrophages (Fixed): engulf damaged and dead cells by phagocytosis
-immune cell
-derived from monocytes
E. free macrophages: wander rapidly through the connective tissue
-called monocytes when circulating in blood
F. mast cells: another immune cell
-synthesize and secrete histamine - inflammation response
-synthesize and secrete heparin - inflammation response
G. lymphocytes - immune cells (T and B cells)
-differentiate into plasma cells (type of B cells) - antibodies
-differentiate into T cell subtypes - assist B cells

34. Connective tissue Matrix fibers: collagen, reticular and elastic
1. Collagen fibers: long, straight and unbranched fibers made of CN type I
-very concentrated and dense in tendons and ligaments
-long chains of collagen protein subunits forming a triple helix
-these helices are wound together - “rope” or a bundle = fibril
-fibrils are then stacked together = collagen fiber
-triple helix – three subunits = 2 alpha 1 chains + 1 alpha 2 chain
e.g. CNI - 2 chains of CNIa1 and one chain of CNIa2
-there are nineteen types of collagen in the body = 80-90% are CNI, CNII
& CNIII

35. Connective tissue: fibers
2. Reticular: made of collagen type III
-2 collagen III alpha1 + 1 collagen III alpha2 subunits = reticular fiber
-reticular fibers interact in a different way – crosslinked to form a 3D network
rather than bundles like collagen type I
-thinner than collagen type I fibers - more flexible
-reticular fibers often have carbohydrates associated with them
-abundant in the walls of hollow organs
-form a supportive stroma (3D network) that supports the functional
cells of these organs
3. Elastic: primarily made up of the proteins fibrillin & elastin
-branching and wavy in appearance

36. Classification

37. The way I organize Connective tissues
Loose – areolar, fat & reticular
Dense – dense (regular, irregular), elastic
Supportive – bone & cartilage
Fluid – blood
Embryonic: first to appear = mesenchyme
-derived from mesoderm germ layer
-cells are star-shaped
-matrix - fine protein filaments
-Mucus connective tissue - jelly-like, many regions of embryo

38. Loose connective tissues: types
1. Areolar tissue
-cells:mainly fibroblasts, spaced far apart
-matrix: sparse collagen fibers, elastic fibers, mostly ground substance
-cushions structrures and can be distorted due to loose organization
e.g. subcutaneous tissue found beneath the dermis

40. 2. Adipose tissue = fat
-cells = adipocytes (fat storing fibroblasts) – derived from pre-adipocytes
-stores triglycerides as a single fat droplet
-matrix: collagen IV – surrounds the individual adipocytes
-cushions joints and organs, stores energy, insulates, secretes hormones
-two types: white and brown (heat production)
-found in the subcutaneous layer under the dermis
liposuction: suction assisted lipoplasty
-removal of SQ fat

42. 3. Reticular:
-thin collagen fibers (reticular fibers) in a 3D network
-supports walls of certain organs
e.g. liver, spleen

43. Dense connective tissues: types
-most of the tissue is densely packed extracellular matrix fibers of
collagen type I
-often called collagenous tissue or fibrous tissue
-type types: 1) dense regular - dense, elastic
e.g. tendons, ligaments
2) dense irregular - interwoven meshwork or fibers
-e.g. dermis of skin, perichondrium of joints
and periosteum of bone

44. 1. Dense Regular :
-cells: few fibroblasts
-matrix: multiple, closely packed collagen I fibers PLUS a fine network of elastic fibers
-very well organized matrix
e.g. tendons, ligaments

45. 2. Dense Regular & Irregular:
-cells: few fibroblasts
-matrix: collagen I fibers PLUS a fine network of elastic fibers with very little organization
e.g. dermis of the skin

46. Dense irregular tissue

47. 2. Elastic:
-yellow, elastic fibers in parallel or branching networks
-walls of larger vessels, airways, hollow organs

48. Supportive Connective tissues: types
-cartilage & bone
1. Cartilage:
-cells = chondrocytes
-matrix = collagen II fibers embedded in a gel-like ground-substance
-ground substance - water + proteoglycans
-proteoglycans – core protein (aggrecan) + sugars
called glycosaminoglycans
e.g. chondroitin sulfate, glucosamine
-functions in support, attachment, protection
-in developing child - model for future bone development (endochondral bone)
- is an avascular tissue - produces anti-angiogenic chemicals (inhibits growth of blood vessels)
-therefore diffusion is the main mode of transport
Proteoglycan

49. -3 types: 1) Hyaline - most common
- “glassy” ECM of collagen II and ground substance
- ends of bones, within joints (synovial, articular),
- end of nose, supports respiratory passages
- when at the ends of bones in a synovial joint = synovial or
articular

50. 2. Elastic - flexible cartilage
-elastic fibers embedded within the ECM
- external ears and parts of larynx

51. 3. Fibrocartilage - very tough -> collagen I fibers within the ECM
- shock absorber
e.g. intervertebral discs
meniscus of the knee

52. Supportive Connective tissues: types
2. Bone = osseous tissue
-most rigid connective tissue
-cells = osteoblasts, osteocytes
-matrix = collagen type I, proteoglycans, other specialized bone proteins
-secreted by osteoblasts – as an unmineralized matrix = osteoid
-mineralized as the OBs mature into osteocytes
-osteocytes are found in lacunae
-matrix is laid in concentric circles = lamellae
-if lamellae surrounds a central canal = Osteon

53. -two types of bone – when the matrix classified by histology
1. Compact - shaft of long bones, outer layer of short, flat
and irregular bones
-very dense appearing bony matrix
-matrix is made up of units called osteons

56. 2. Spongy - ends of bones, middle layer of short, flat
and irregular bones
-thin bars or “plates” (called trabeculae) of bone separated by irregular spaces filled with red marrow
-lighter than compact – yet stronger

57. Fluid Connective tissue: Blood
-cells suspended in a fluid matrix = plasma
-plasma ~ 55% blood volume
-inorganic salts
-organic substances - e.g. sugars, proteins
-cells: 1) RBCs - biconcave, disc-shaped
-contains hemoglobin - 4 globin proteins
+ heme group (iron)
2) WBCs - fight infection
= leukocytes
- many types: a. monocytes/macrophages
b. lymphocytes - T and B cells
c. basophils - histamine
d. neutrophils - 1st at infection
e. eosinophils - allergic response
3) platelets - blood clotting response

58. Muscular Tissue specialized for contraction
very distinct organelles within the cells
3 types
1. skeletal – voluntary muscle
2. cardiac – involuntary muscle
3. smooth – involuntary muscle

59. 3 types of Muscle tissue:
1) striated/skeletal – voluntary nervous control
-repeating banding patterns of actin & myosin = striated appearance
-mature muscle cells = muscle fibers
- very long, multi-nucleated cells – made from fusion of myoblasts
-muscle cells/fibers cannot divide – but new cells form from differentiation of myogenic stem cells = satellite cells
-attached to bones via tendons

60. 2) cardiac - involuntary control
- only found in heart
-cells are striated but uni-nuclear = cardiomyocytes
-incapable of dividing – PLUS there are no satellite cells
-therefore damaged heart muscle cannot be regenerated

61. -cardiomyocytes are connected end to end by intercalated discs
-these discs are areas of communication between cardiocytes through gap junctions
-the discs also help channel the forces of contraction

62. 3) smooth – involuntary control
-lines blood vessels, airways and organs
-control their own rate of contraction through action of pacemaker cells
-nervous system can also control contraction
-slow, sustained contraction
-non-striated, spindle shaped cells - single nucleus
-capable of division and can regenerate damaged tissue after injury through simple division ???

63. SMOOTH
DENSE
-you could confuse dense irregular connective tissue and smooth muscle – so
be careful!!
-there are more cells/nuclei in smooth muscle

64. Neural Tissue (Nervous Tissue)
specialized for the conduction of electrical impulses from one body
region to another
two types of neural cells:
1) neurons
2) glial cells
1) glial cells: e.g. astrocytes, oligodendrocytes, microglia, Schwann cells
-supportive function to neurons
-differ depending whether they are found in the CNS or PNS

65. 2) neuron:
- cell body (soma), dendrites, axon with axon terminals and synaptic end bulbs
-therefore the neuron has polarity
-capable of generating an electrical signal = action potential
-dendrite receives and/or generates the action potentail
-axon - conducts the nerve impulse
-forms a synapse with another neuron or a muscle cell