1. Human Anatomy and Physiology
Histology
Human Anatomy and Physiology

2. What Is a Tissue? Tissue = cells organized into layer or groups
Cells separated by nonliving, intercellular materials
Solid minerals in bone
Liquid plasma in blood

3. How Are Tissues Maintained?
Stem cells = cells that have the ability to divide many times and yield new cells that then specialize
Groups of stem cells set aside in tissues to replace worn or damaged parts

4. 4 Major Types of Tissues

5. Embryonic Germ Layers

6. General Characteristics of Epithelial Tissue
Widespread throughout the body
Basement membrane
Lacks blood vessels
Divides readily
Tightly packed
Classified according to shape and number of layers
Widespread - Covers organs, forms inner lining of body cavities, and lines hollow organs
Basement membrane - Always has a free surface exposed to outside of body or an internal open space – basement membrane anchors underside of epithelial tissue to connective tissue
No blood vessels – nutrients diffuse to epithelium from underlying connective tissue
Divide readily – some epithelial tissues are constantly damaged and replaced (skin, stomach lining)
Tightly packed – little intracellular material, many desmosomes, effective barriers
Classification – squamous, cuboidal, and columnar; simple and stratified

7. Simple Squamous Epithelium
Single layer of thin, flattened cells that fit tightly together; broad and thin nuclei
Damaged easily because of thinness

8. Simple Squamous continued…
Functions:
Allows substances to pass easily
Forms walls of capillaries
Lines air sacs (alveoli) of lungs
Lines insides of blood and lymph vessels
Covers membranes that line body cavities

9. Simple Cuboidal Epithelium
Single layer of cube-shaped cells; centrally located and spherical nucleus

10. Simple Cuboidal continued…
Functions:
Covers the ovaries
Lines the kidney tubules
Lines ducts of the salivary glands, pancreas, and liver
Secretion and absorption
In kidneys, functions in secretion and absorption
In glands, secretes glandular products

11. Simple Columnar Epithelium
May be ciliated or nonciliated
Goblet cells
Microvilli
Functions:
Absorption
Movement of substances
Secretion
Single layer of elongated cells; nuclei usually at same level near basement membrane
May be ciliated or nonciliated
May have goblet cells between columnar epithelial cells; goblet cells – flask shaped, glandular cells that secrete mucus (protective fluid)
If specialized for absorption, may have microvilli on surface to increase surface area; cylinder shaped processes

12. Nonciliated Simple Columnar Epithelium
Lines uterus and parts of the digestive tract (stomach, small intestines, large intestine, galbladder)
Elongated cells form thick tissue that provides protection to underlying tissue
Secretes digestive fluids and absorbs nutrients from digested foods

13. Ciliated Simple Columnar Epithelium
Cilia used to move substances (egg cells through oviducts)
Lines oviducts, small bronchi

14. Pseudostratified Columnar Epithelium
Appear stratified but all cells reach the basement membrane
Appear layered because nuclei are at two or more levels
Cells often fringed with cilia
Goblet cells scattered throughout

15. Pseudostratified Columnar continued…
Functions:
Lines the passages of the respiratory system
Lines ducts of glands and sperm-carrying ducts
In respiratory tract, mucus traps dust and microorganisms that enter with air and cilia move mucus up and out of airways

16. Stratified Squamous Epithelium
Stratified epithelium is named for the shape of the cells on the outermost layers
Stratified squamous is made of many layers, so it’s relatively thick
Deeper cells tend to be more cuboidal or columnar
Stratified layers grow from the basement membrane
Keratinized or nonkeratinized – keratinized contains keratin and produces a dry, tough, protective material and outer layer is dead; nonkeratinized stays soft and moist

17. Stratified Squamous continued…
Functions:
Keratinized form makes up the epidermis
Nonkeratinized lines the oral cavity, throat, vagina, and anal canal

18. Stratified Cuboidal Epithelium
Functions:
Lines larger ducts of mammary glands, sweat glands, salivary glands, and pancreas
Forms lining of developing ovarian follicles and seminiferous tubules
Consists of 2-3 layers of cuboidal cells

19. Stratified Columnar Epithelium
Functions:
Lines vas deferens and some parts of the pharynx
Protection
Secretion
Basal cells are usually cuboidal, but superficial cells are columnar
Rare in the body

20. Transitional Epithelium
Specialized to change in response to increased tension; appears thinner when stretched
Resembles both stratified squamous and stratified cuboidal
Basal cells are usually columnar and superficial cells are squamous or dome-shaped depending on the degree of stretch

21. Transitional Epithelium continued…
Functions:
Forms the inner lining of the urinary bladder
Lines the ureters and part of the urethra
Expandable lining
Blocks urine from diffusing back into the body

22. Glandular Epithelium
Specialized to produce and secrete substances into ducts or into body fluids
Glands classified as endocrine or exocrine
Glandular cells usually found within cuboidal or columnar epithelium
Gland = one or more glandular cells
Exocrine glands can also be classified according to their structure: unicellular, simple, compound
Simple gland – unbranched duct
Compound gland – branched duct
Tubular gland – epithelial-lined tubes
Alveolar glands – saclike portions on ends
Most exocrine glands are merocrine: cells glands – watery secretion, mucous cells – thicker fluid

23. Endocrine Glands
Pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas
Will be discussed in more detail later

24. Exocrine Glands Goblet cells
Intestinal glands, sweat glands, mucous glands in small intestine, sebaceous glands, bulbourethral glands of male, salivary glands

25. Classification of Connective Tissue

26. Mesenchyme
Embryonic connective tissue that gives rise to all connective tissues
Consists of ground substance (gel-like), fibers, and star-shaped mesenchymal cells

27. General Characteristics of Connective Tissue
Most abundant type of tissue by weight
Large amounts of matrix between cells
Matrix contains fibers and ground substance
Vascularity
Major cell types:
Fibroblast
Macrophage
Mast Cell
Fiber types:
Collagenous
Elastic
Reticular
Connective tissue proper and specialized connective tissues
Functions: bind structures, provide support and protection, frameworks, fill spaces, store fat, produce blood cells, protext against infections, help repair tissue damage
Ground substance consistency varies from fluid to semisolid to solid; ground substance binds, supports, and provides a medium through which substances may be transferred between the blood and tissue cells
Generally have good blood supplies
Fibroblast – most common kind of fixed cell in connective tissues; large, star-shaped; produce fibers by secreting protein into the matrix of connective tissues
Macrophage – usually attached to fibers but may move around; specialized to carry on phagocytosis; role in immunity
Mast cells – large and widely distributed; usually located near blood vessels; release heparin (prevents blood clotting) and histamine (promotes reactions associated with inflammation and allergies)
Collagenous fibers – thick threads of collagen; grouped in long, parallel bundles; dense and loose connective tissue classified according to amounts of collagenous fibers; sometimes called white fibers
Elastic fibers – bundles of microfibrils embedded in elastin (protein); fibers branch and form complex networks; weaker than collagenous fibers but very elastic; common in body parts that stretch; sometimes called yellow fibers
Reticular fibers – very thin collagenous fibers; highly branched and form delicate supporting networks

28. Areolar Connective Tissue
Also known as loose connective tissue
Mainly fibroblasts
Collagenous and elastic fibers

29. Areolar Connective Tissue continued…

30. More Areolar Connective Tissue
Functions:
Binds the skin to underlying organs
Fills spaces between muscles
Lies beneath most epithelium layers
Blood vessels nourish epithelial cells

31. Adipose Tissue Also known as fat
Adipocytes store fat in their cytoplasm
Amount in the body reflects diet or endocrine disorder
Adipocytes resemble fibroblasts until they accumulate fat and swell; nucleus is pushed to the side
Adipose tissue forms when adipocytes crowd out other cells
A person is born with a certain number of fat cells
Fasting causes adipocytes to lose fat droplets and shrink

32. Adipose Tissue continued…
Functions:
Lies beneath skin, in spaces between muscles, around the kidneys, behind the eyeballs, in some abdominal membranes, on the surface of the heart, in breasts, and around some joints
Cushions joints and some organs
Insulation
Stores energy

33. Reticular Connective Tissue
Reticular fibers
Numerous fibroblasts and white blood cells

34. Reticular Tissue continued…
Function:
Provides supportive framework in walls of certain internal organs, such as the liver, spleen, and lymphatic organs

35. Regular Dense Connective Tissue
Closely packed collagenous fibers, fine network of elastic fibers
Few cells, mostly fibroblasts
Regular dense connective tissue – very organized fibers

36. Regular Dense continued…
Functions:
Attaches muscles to bones or to other muscles
Attaches bones to bones
Withstands great tensile stress when pulling force is applied in one direction
Makes up tendons and most ligaments
Poor blood supply, so tissue repair takes longer – sprains take considerable amount of time to heal

37. Irregular Dense Connective Tissue
Thicker, interwoven, and more randomly organized fibers
Same fiber types and cell types as regular dense connective tissue

38. Irregular Dense continued…
Functions:
Able to withstand tension exerted in many directions
Provides structural strength
Makes up dermis of skin, submucosa of digestive tract, fibrous capsules

39. Elastic Connective Tissue
Elastic fibers in parallel strands or branching networks
Collagenous fibers and fibroblasts between elastic fibers
Found in ligamenta flava and within walls of some large arteries, some portions of the heart, and larger airways
Ligamenta flava = attachments between vertebrae of the spinal column

40. Cartilage Rigid connective tissue Functions: Many collagenous fibers
Provides support, frameworks, and attachments
Protects underlying tissues
Forms structural models for developing bones
Many collagenous fibers
Chondrocytes and lacunae
Perichondrium
Lacks direct blood supply
Types distinguished by types of intercellular material
Chondrocytes are cartilage cells that occupy small chambers called lacunae
Perichondrium is connective tissue covering that encloses a cartilaginous structure; contains blood vessels
Lack of direct blood supply means cartilage heals very slowly and chondrocytes divide infrequently

41. Hyaline Cartilage Most common type of cartilage
Collagenous fibers form imperceptible network
Chondroblasts form matrix and mature into chondrocytes

42. Hyaline Cartilage continued…
Functions:
Supports and reinforces
Has resilient cushioning properties
Resists compression stress
Found on ends of bones in joints, soft part of nose, trachea, larynx, and costal cartilages of ribs
Forms most of embryonic skeleton
Important in bone growth and repair of fractures

43. Elastic Cartilage More flexible than hyaline cartilage
Elastic fibers in matrix

44. Elastic Cartilage continued…
Functions:
Maintains the shape of a structure while allowing greater flexibility
Provides the framework for the external ears and parts of the larynx

45. Fibrocartilage
Very tough cartilage
Many large collagenous fibers

46. Fibrocartilage continued…
Functions:
Tensile strength
Shock absorber
Forms intervertebral disks, disks in knee joint, and pubic symphysis

47. Compact Bone Also called osseous tissue Most rigid connective tissue
Mineral salts in matrix
Large amounts of collagen
Osteocytes
Hardness due to mineral salts in matrix – calcium phosphate and calcium carbonate
Osteocytes are bone cells; deposit bone matrix in thin layers called lamellae which form rings around capillaries located within central (Haversian) canals
Osteocytes located within lacunae
Haversian system = osteocytes, lamellae, and central canal
Each central canal contains a blood vessel – good blood supply
Canaliculi = small tubes in matrix that contain cytoplasmic extensions of bone cells

48. Bone continued… Functions: Supports and protects by enclosing
Provides levers for muscles to act on
Stores calcium and other minerals
Marrow inside bones is site of hematopoiesis

49. Blood Blood plasma Red blood cells, white blood cells, and platelets
Most blood cells formed in red bone marrow
Functions: transport gases, fight infection, clotting
Will be discussed in more detail later
Blood plasma = fluid matrix of blood tissue

50. General Characteristics of Muscle Tissues
Contractile
Elongated cells
Three types classified according to striations and nuclei
Will be discussed more later

51. Skeletal Muscle Long and narrow cells Striations Multinucleate cells
Striations = alternating light and dark cross-markings on cells

52. Skeletal Muscle continued…
Functions:
Voluntary movement
Locomotion
Manipulation of the environment
Facial expression
Voluntary control
Attached to bones and occasionally skin

53. Smooth Muscle No striations Spindle-shaped cells
Single, centrally located nucleus

54. Smooth Muscle continued…
Functions:
Propels substances or objects along internal passageways
Involuntary
Found mostly in walls of hollow organs

55. Cardiac Muscle Striated cells joined end to end
Cells form complex, branching network
Intercalated disks
Usually uninucleate
Intercalated disks are specialized junctions between cardiac muscle cells

56. Cardiac Muscle continued…
Functions:
Involuntary
Propels blood into the circulation
Found only in the heart

57. General Characteristics of Nervous Tissue
Neurons
Neuroglia
Will be discussed more later
Neurons – nerve cells; highly specialized; sense changes in their surroundings and respond by transmitting nerve impulses to other neurons, muscles, or glands
Neuroglia – cells that support and bind the components of nervous tissue, carry on phagocytosis, and help supply nutrients to neurons by connecting them to blood vessels

58. Nervous Tissue continued…
Functions:
Transmits electrical signals from sensory receptors and to effectors (muscles and glands)
Found in brain, spinal cord, and nerves