Histology and anatomy

1. 5-1
Chapter 5
Histology

2. 5-2
Histology
• Study of Tissues
• Epithelial Tissue
• Connective Tissue
• Nervous and Muscular Tissue
• Intercellular Junctions, Glands and
Membranes
• Tissue Growth, Development, Death and
Repair

3. 5-3
• Histology -
• Tissue -
• Organ-
Aka microscopic anatomy
•study of tissues and
how they are arranged
into organs
structures with discrete boundaries,
composed of 2 or more tissue types
Composed of similar cells and
cell products which
• arose from same region of embryo

4. 5-4
The Study of Tissues
• 200 Different cell types
• Four primary tissue classes (Table)
1. epithelial tissue
2. connective tissue
3. muscular tissue
4. nervous tissue

5. 5-5
Features of Tissue Classes
• Differences between tissue classes
– 1. types and functions of cells
– 2. characteristics of matrix (extracellular material)
• fibrous proteins
• ground substance
– 3. space occupied by cells versus matrix
– connective tissue cells are widely separated
– little matrix between epithelial and muscle cell

6. 5-6

7. 5-7
Embryonic Tissues
• Embryo begins as single cell
– divides into many cells and layers (strata)
• 3 Primary germ layers
• forms epidermis and nervous system
• forms mucous membrane lining GI tract and respiratory system
and digestive glands
• gives rise to muscle, bone, blood
ectoderm (outer)
endoderm (inner)
mesoderm (middle) becomes mesenchyme

8. 5-8

9. 5-9
Interpreting Tissue Sections
• Preparation of histological specimens
• fixative prevents decay (formalin)
• sliced into thin sections 1 or 2 cells thick
• mounted on slides and colored with histological stain
– stains bind to different cellular components
•Sectioning reduces 3-dimensional structure
to 2-dimensional slice
In your mind, try to convert the microscopic image
to a mental image of the WHOLE structure.

10. 5-10
• Sectioning a cell
with a centrally
located nucleus
• Some slices
miss the cell
nucleus
• In some the
nucleus is
smaller
Interpreting Tissue sections

11. 5-11
Sectioning Hollow Structures
• Cross section of
blood vessel, gut,
or other tubular
organ.
• Longitudinal
section of a sweat
gland. Notice
what a single slice
could look like.

12. 5-12
Types of Sections
• Longitudinal section
– tissue cut along
longest direction of
organ
• Cross section
– tissue cut
perpendicular to length
of organ
• Oblique section
– tissue cut at angle
between cross and
longitudinal section

13. 5-13

14. 5-14

15. 5-15
Epithelial Tissue

16. 5-16
Epithelial Tissue
Properties:
• Layers of closely adhering cells
• Flat sheet with upper surface exposed to the
environment or an internal body cavity
• No blood vessels
– underlying connective tissue supplies oxygen
• Rests on basement membrane
Cover body surfaces, line body cavities, for external &
internal lining of many organs, & constitute many
gland tissue.

17. 5-17
Basal Lamina
Reticular Lamina

18. 5-18
Function of the Basement Membrane
1. Filter (i.e. to prevent passing of
bacteria)
2. Attach Cells (i.e. Hemidesmosomes)
3. Limits Stretch (i.e. reduce damage to
cells)

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Epithelial Tissue
• Classified into two broad categories:
1. Simple – every cell touches the basement
membrane;
2. Stratified – some cells rest on other cells and do
not contact the BM.

20. 5-20
Simple Epithelia Tissue
4 types, 3 named by the cell type:
1. Simple Squamous –
2. Simple Cuboidal –
3. Simple Columnar –
4. Pseudostratified Columnar-
Tall narrow cells
Thin scaly cells
square or round cells
Not all cells reach the free surface

21. 5-21
Stratified – layers, cell layered on cells
4 types, 3 named for their surface cells:
Stratified Squamous-
Stratified Cuboidal-
Stratified Columnar-
Transitional Epithelium -
Thin surface cells
Square or round surface cells
Tall or narrow surface cells
Transition stage between stratified squamous
and columnar surface cells
Stratified Epithelia Tissue

22. 5-22
Stratified Epithelia
- More than one layer of cells
- Named for shape of surface cells
- Deepest cells on basement membrane
Characterized by:
1. Basal Layer- First layer of cells on BM (best O2
supply)
2. Intermediate layer(s)- any layer between basal and superficial
layers. Size diminishes with increase diffusion distance.
3. Superfical Layer- Top (oldest ) layer of cells. The shape of these
cells determines the name of tissue.

23. 5-23
Basal Cells (layer)
Superficial Layer
Intermediate Layer
Wide spread epithelium in the body? Stratified squamous epithelium
Start cuboidal → squamous → exfoliate (desquamation)

24. 5-24
Stratified Squamous Epithelia
2 Types:
1. keratinized epithelium:
- found on skin surface (compact, dead squamous
cells);
- packed with protein keratin and coated with water
repellent;
Functions
- retards water loss
- resists penetration by disease organisms

25. 5-25
Stratified Squamous Epithelia
2. Nonkeratinized epithelium:
- lacks surface of dead cells,
- abrasion-resistant,
- provides a moist slippery environment,
-tongue, esophagus, vagina & other internal
organs

26. 5-26
Simple VS Stratified Epithelia
• Simple epithelium
– contains one layer of cells
– named by shape of cells
• Stratified epithelium
– contains more than one layer
– named by shape of apical cells

27. 5-27
Identify Epithelium Type
Simple Cuboidal

28. 5-28
Identify Epithelium Type
Simple Columnar

29. 5-29
Identify Epithelium Type
?
Simple squamous

30. 5-30
Identify Epithelium Type
Pseudostratified Columnar

31. 5-31
Identify Epithelium Type
Stratified Columnar

32. 5-32
Identify Epithelium Type
Stratified Cuboidal

33. 5-33
Structural and Functional differences of
Simple Epithelia and Stratified Epithelia

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Simple Squamous Epithelium
• Single row of flat cells
• Permits diffusion of substances
• Secretes serous fluid
• Alveoli, glomeruli, endothelium, and serosa

35. 5-35
Simple Cuboidal Epithelium
• Single row cube-shaped cells with microvilli
• Absorption and secretion, mucus production
– Absorptive cells usually have microvilli (striated or brush borders)
– Function:
• Liver, thyroid, mammary and salivary glands,
bronchioles, and kidney tubules
increase surface area

36. 5-36
Simple Columnar Epithelium
• Single row tall, narrow cells
– oval nuclei in basal half of cell
• Absorption and secretion; mucus secretion
• Lining of GI tract, uterus, kidney and uterine tubes

37. 5-37
Pseudostratified Epithelium
• Single row of cells some not reaching free
surface
– nuclei give layer stratified look
• Secretes and propels respiratory mucus

38. 5-38
Keratinized Stratified Squamous
• Multilayered epithelium covered with dead
squamous cells, packed with keratin
– epidermal layer of skin
• Retards water loss and barrier to organisms

39. 5-39
Nonkeratinized Stratified Squamous
Multilayered surface epithelium forming moist,
slippery layer
Tongue, oral mucosa, esophagus and vagina

40. 5-40
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

41. 5-41
Transitional Epithelium
• Multilayered epithelium surface cells that change
from round to flat when stretched
– Function:
– allows for filling of urinary tract
– ureter and bladder
Protection from stretch

42. 5-42
Connective Tissue

43. 5-43
Connective Tissue
This category includes:
- Fibrous Tissue- Most diverse, contains fibers, cells,
ground substances.
- Fat
- Cartilage
- Bone
- Blood

44. 5-44
Connective Tissue Overview
Most abundant and variable tissue type;
Widely spaced cells separated by fibers and ground
substance;
Functions:
1. Binding of organs: tendons bind muscle to bone, fat holds kidneys
and eyes in place;
2. Support: bones support the body;
3. Physical protection: cranium protect brain;
4. Immune protection: CT cells attack foreign invaders;
5. Movement: cartilages are involved in movement of vocal cords;
6. Storage: bone is a reservoir of calcium;
7. Heat production: brown fat generates heat in infants;
8. Transport: blood transports gases, nutrients etc.

45. 5-45
Fibrous Connective Tissue
Most diverse type of connective tissue;
aka fibroconnective tissue;
Fibrous Connective Tissue contains:
- fibers
- cells
- ground substance

46. 5-46
Components of Fibrous Connective Tissue
Cells of Fibrous 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

47. 5-47
Fibers of Connective Tissue
3 Common Types
1. Collagen fibers (white fibers)
– tough, stretch resistant, yet flexible
– tendons, ligaments and deep layer of the skin
1. Reticular fibers
– Early stages of healing, (produce fibroblasts)
– framework in spleen and lymph nodes
1. Elastic fibers (yellow fibers)
– thin branching fibers of elastin protein
– stretch and recoil like rubberband (elasticity)
– skin, lungs and arteries stretch and recoil

48. 5-48

49. 5-49

50. 5-50
Connective Tissue Ground Substance
• Gelatinous material between cells
– absorbs compressive forces
• Consists of 3 classes of large molecules:
1. glycosaminoglycans – chondroitin sulfate
•disaccharides that attract sodium and hold water
•role in regulating water and electrolyte balance
2. Proteoglycan (bottlebrush-shaped molecule)
•create bonds with cells or extracellular macromolecules
3. adhesive glycoproteins
•protein-carbohydrate complexes bind cell membrane to
collagen outside the cells

51. 5-51
Fibrous Connective Tissue Types
Divided into 2 Broad categories according to
fiber content:
1. Loose connective tissue
– gel-like ground substance between cells
– types
i. areolar
ii. reticular
iii. adipose
2. Dense connective tissue
– fibers fill spaces between cells
– types vary in fiber orientation
i. dense regular connective tissue
ii. dense irregular connective tissue

52. 5-52
Areolar Tissue
• Loose arrangement of fibers and cells in abundant
ground substance
• Underlies all epithelia, between muscles,
passageways for nerves and blood vessels

53. 5-53
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

54. 5-54
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

55. 5-55
Dense Regular Connective Tissue
• Densely, packed, parallel collagen fibers
– compressed fibroblast nuclei
• Tendons and ligaments hold bones together and
attach muscles to bones

56. 5-56
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

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Marfan Syndrome

58. 5-58
Cartilage
• Supportive connective tissue with rubbery matrix
• Chondroblasts produce matrix that surround the
cell forming a cavity called a lacunae.
– 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

59. 5-59
Hyaline Cartilage
• Rubbery matrix; dispersed collagen fibers; clustered
chondrocytes in lacunae (small cavity)
– supports airway, eases joint movements
• Ends of bones at movable joints; sternal ends of ribs;
supportive material in larynx, trachea, bronchi and fetal
skeleton

60. 5-60
Elastic Cartilage
• Hyaline cartilage with elastic fibers
• Provides flexible, elastic support
– external ear and epiglottis

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Fibrocartilage
• Hyaline cartilage with extensive collagen fibers
• Resists compression and absorbs shock
– pubic symphysis, meniscus and intervertebral discs

62. 5-62

63. 5-63
Bone
Bone has two meanings:
1) Refers to a structure
2) Bone Tissue or Osseous Tissue

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Osseous Tissue
2 Forms:
1. Spongy bone - spongy in appearance
a) delicate struts of bone
b) covered by compact bone
c) found in heads of long bones
2. Compact bone - solid in appearance
a) more complex arrangement
b) cells and matrix surround vertically oriented
blood vessels in long bones

65. 5-65
Bone Tissue (compact bone)
• Calcified matrix in lamellae around central canal
• Osteocytes in lacunae between lamellae
• Skeletal support; leverage for muscles; mineral
storage

66. 5-66
Blood
(Fluid Connective Tissue)
• 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

67. 5-67
Erythrocytes: aka RBC, most abundant, no nuclei
Leukocytes: aka WBC, defense against infection and
other diseases. 5 types distinguished by nuclear shape,
neutrophils, eosinophils, basophils, lymphocytes, and
monocytes.
Platelets: clotting, minimize blood loss, secret growth
factors that promote blood vessel growth and maintanence.

68. 5-68
Never Let Monkeys Eat Bananas
{neutrophils, lymphocytes, monocytes,
eosinophils, basophils}

69. 5-69
Excitable Tissues
All cells have this characteristic but it is
developed to a higher degree in nervous and
muscular tissue.
Excitation is due to electrical charge difference
called a membrane potential.

70. 5-70
Nerve Tissue
• Large cells (neurons) with long cell processes
– surrounded by smaller glial cells lacking processes
– Glial (neuroglia) cells protect and assist neurons
• Internal communication between cells
– in brain, spinal cord, nerves and ganglia

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Axon
Dendrite
Soma
Glial Cells

72. 5-72
Muscle Tissue
Elongated cells stimulated to contract
• Exert physical force on other tissues
– 1. move limbs
– 2. push blood through a vessel
– 3. expel urine
– 4. breathing, speech
Source of body heat
3 histological types of muscle
– skeletal, cardiac and smooth

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Skeletal Muscle
• Long, cylindrical, unbranched cells with
striations and multiple peripheral nuclei
– movement, facial expression, posture, breathing,
speech, swallowing and excretion
– Considered striated and VOLUNTARY

74. 5-74
Smooth Muscle
• Short fusiform cells; nonstriated with only one central
nucleus (aka Visceral Muscle)
– Considered INVOLUNTARY
– 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. 5-75
Cardiac Muscle
• Short branched cells with striations and
intercalated discs
– one central nuclei per cell
– Considered INVOLUNTARY
• Pumping of blood by cardiac (heart) muscle

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Intercellular Junctions, Glands and
Membranes

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All cells (except blood) anchored to each other or their
matrix by intercellular junctions
3 Types
Intercellular Junctions
1. Tight Junctions
2. Desemosomes
3. Gap Junctions

78. 5-78
Encircle the cell joining it to surrounding cells
– zipperlike complementary grooves and ridges
Prevents passage between cells, ensure
passage through cells
– GI and urinary tracts
Tight Junctions

79. 5-79
Patch between cells holding them together by glycoprotein filaments.
– Enables tissue to resist mechanical stress
– Hemidesmosomes on basal cell of epithelial tissue
Uterus, heart and epidermis
Desmosomes

80. 5-80
Ring of transmembrane proteins form a water-filled channel
– small solutes pass directly from cell to cell (ions, glucose, AA);
– in embryos, nutrients pass from cell to cell until circulatory system
develops;
– cardiac and smooth muscle (ion flow for excitation).
Gap (communicating) Junctions

81. 5-81
Pemphigus Vulgaris

82. 5-82
Glands
Are cells or organs that secrete substances for use
elsewhere in the body or releases them
for elimination from the body. --- Saladin, 4th
ed.
Glands are predominately epithelial tissue.
Classified as Endocrine or Exocrine.

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Endocrine and Exocrine Glands
1. Exocrine glands connect to surface with a duct
(epithelial tube)
2. Endocrine glands secrete (hormones) directly into
bloodstream
• Mixed organs do both
– liver, gonads, pancreas
3. Unicellular glands – are secretory cells found in
nonsecretory epithelia (endo or exocrine)
– goblet cells in respiratory tract

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Exocrine Gland Structure
Capsule- encloses most glands, forms septa that produces
lobes
Stroma = connective tissue that supports and organizes the
gland.
Parenchyma = collection of cells that synthesis & secrete
Found in:
mammary glands
Pancreas
Salivary glands

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Exocrine Glands Classification
• Simple glands - unbranched duct
• Compound glands - branched duct
• Shape of gland
– acinar - secretory cells form dilated sac
– tubuloacinar - both tube and sacs

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Modes of Exocrine Secretion
Classified depending on how they produce their
secretions:
1. Merocrine gland:
2. Holocrine gland:
3. Apocrine gland:
release their product by exocytosis
i.e.: tears, gastric glands, pancreas,
etc.
Secretory cells disintegrate to deliver their accumulated product
•oil-producing glands of the scalp
Primary merocrine, but differ histologically
and function. Ie. Axillary (armpit) sweat.

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Modes of Exocrine Secretion

88. 5-88
Modes of Exocrine Secretion

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Tissue Growth, Development, Death
and Repair

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Tissue Growth
Hyperplasia =
Hypertrophy =
Neoplasia =
tissue growth through cell
multiplication
Enlargement of preexisting cells
•Muscles grow through exercise
Growth of a tumor (benign or malignant)
through growth of abnormal tissue

91. 5-91
A.
C.
B.
Endometriosis, also known as endometrial
hyperplasia, is a condition in which the
endometrial tissue grows outside the uterus,
causing scarring, pain, and heavy bleeding.
It can often damaging the fallopian tubes
and ovaries in the process. A common
organic cause of infertility, endometriosis
can be treated with medications such as
lupron for endometriosis that lowers
hormone levels and decreases endometrial
growths.

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Tissue Shrinkage and Death
1. Atrophy = loss of cell size or number
a) disuse atrophy from lack of use (leg in a cast)
2. Necrosis = pathological death of tissue
a) gangrene - insufficient blood supply
b) gas gangrene - anaerobic bacterial infection
c) infarction - death of tissue from lack of blood
d) decubitus ulcer - bed sore or pressure sore
3. Apoptosis = programmed cell death
a) cells shrink and are phagocytized (no
inflammation)

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94. 5-94
Changes in Tissue Types
Tissues can change types:
1. Differentiation
– unspecialized tissues of embryo become
specialized mature types
• mesenchyme to muscle
1. Metaplasia
– changing from one type of mature tissue to
another
• simple cuboidal tissue of vagina before puberty
changes to stratified squamous after puberty

95. 5-95
Tissue Repair
Tissues can be repaired by 2 means:
1. Regeneration
– replacement of damaged cells with original cells
– skin injuries and liver regenerate
2. Fibrosis
– replacement of damaged cells with scar tissue
• function is not restored
– healing muscle injuries, scarring of lung tissue in TB or
healing of severe cuts and burns of the skin
– keloid is healing with excessive fibrosis
(raised shiny scars)

96. 5-96
Wound Healing of a Laceration
• Damaged vessels leak blood
• Damaged cells and mast
cells leak histamine
– dilates blood vessels
– increases blood flow
– increases capillary
permeability
• Plasma carries antibodies,
clotting factors and WBCs
into wound

97. 5-97
Wound Healing of a Laceration
• Clot forms, loosely
knitting the edges
together;
• Scab forms on surface,
temporarily seals
wound;
• Macrophages start to
clean up tissue debris.

98. 5-98
Wound Healing of a Laceration
• New capillaries grow
into wound
• Macrophages remove
clot while fibroblasts
deposit new collagen
to replace old material
• Fibroblastic phase
(aka reconstructive
phase) begins in 3-4
days and lasts up to 2
weeks

99. 5-99
Wound Healing of a Laceration
• Epithelial cells multiply
(regenerate) and spread
beneath scab;
• Scab falls off;
• Epithelium thickens;
• Connective tissue forms
only scar tissue (fibrosis);
• Remodeling (maturation)
phase may last 2 years.

100. 5-
100
Types of Secretions
• Serous glands
– produce thin, watery secretions
• sweat, milk, tears and digestive juices
• Mucous glands
– produce mucin that absorbs water to form a
sticky secretion called mucus
• Mixed glands contain both cell types
• Cytogenic glands release whole cells
– sperm and egg cells

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101
Mucous Membranes
• Epithelium, lamina propria and muscularis mucosae
• Lines passageways that open to the exterior: reproductive,
respiratory, urinary and digestive
– Mucous (movement of cilia) trap and remove foreign particles
and bacteria from internal body surfaces

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102
Membrane Types
• Cutaneous membrane = skin
– stratified squamous epithelium over connective
tissue
– relatively dry layer serves protective function
• Synovial membrane lines joint cavities
– connective tissue layer only, secretes synovial fluid
• Serous membrane (serosa) –internal membrane
– simple squamous epithelium over areolar tissue,
produces serous fluid
– covers organs and lines walls of body cavities

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103
Stem Cells
• Undifferentiated cells with developmental
plasticity
• Embryonic stem cells
– totipotent (any cell type possible)
• source = cells of very early embryo
– Pluripotent (tissue types only possible)
• source = cells of inner cell mass of embryo
• Adult stem cells (undifferentiated cells in
tissues of adults)
– multipotent (bone marrow producing several
blood cell types)
– unipotent (only epidermal cells produced)

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104
Tissue Engineering
• Production of tissues and organs in the lab
– framework of collagen or biodegradable polyester
fibers
– seeded with human cells
– grown in “bioreactor” (inside of mouse)
• supplies nutrients and oxygen to growing tissue
• Skin grafts already available
– research in progress on heart valves, coronary
arteries, bone, liver, tendons