1. Chapter 5: Tissues

2. Tissues Groups of cells similar in structure and function
The four types of tissues
Epithelial
Connective
Muscle
Nerve

3. Epithelial Tissue Cellularity – composed almost entirely of cells
Covers organs, forms the inner lining of body cavities, & lines hollow organs
Special contacts – form continuous sheets held together by tight junctions and desmosomes
Polarity – apical (free surface side) and basal (thin, non-living basement membrane) surfaces

4. Epithelial Tissue
Supported by connective tissue – reticular and basal laminae
Avascular but innervated – contains no blood vessels but supplied by nerve fibers
Get nutrients and excrete wastes via diffusion
Regenerative – rapidly replaces lost cells by cell division
Ex) skin

5. Classification of Epithelia
Simple (one layer) or stratified (2 or more layers)
Name is based on the apical surface
Functions
Simple – filtration, absorption, secretion
Stratified - protection

6. Classification of Epithelia
Squamous, cuboidal, or columnar
Have hexagon shape
Makes it more efficient

7. Epithelia: Simple Squamous
Single layer of flattened cells with disc-shaped nuclei & sparse cytoplasm
Fit tightly together (floor tiles)
Functions
Diffusion & filtration
Provide a slick, friction-reducing lining in lymphatic and cardiovascular systems
Present in kidney glomeruli, lining of heart, blood vessels, lymphatic vessels, & serosae

8. Epithelia: Simple Squamous
Substances pass pretty easily through it
Ex) lines the air sacs (alveoli) in lungs where oxygen and carbon dioxide are exchanged
Since it is so thin and delicate, it is easily damaged

9. Simple Squamous
Description: single layer of flattened cells with disc-shaped central nuclei & sparse cytoplasm; the simplest of the epithelia
Function: allows passage of materials by diffusion & filtration in sites where protection is not important; secretes lubricating substances in serosae
Location: kidney glomeruli, air sacs of lungs, lining of heart, blood vessels & lymphatic vessels, lining of ventral body cavity (serosae)

10. Simple Squamous Epithelium

11. Simple Cuboidal Epithelium
Single layer of cube-shaped cells
Usually have large, centrally located, spherical nuclei
Present in ovaries, kidney tubules (filtration), & ducts of certain smaller glands like the salivary, thyroid, pancreas, & liver glands
Tissue secretes glandular products

12. Simple Cuboidal Epithelium

13. Simple Columnar Epithelium
Single layer of elongated cells with large, spherical nuclei
Goblet cells are often found in this layer
Secrete mucus for protection on the apical surface
Functions: secretes digestive fluids & absorbs nutrients from digested foods
Found in most organs of the digestive tract (stomach, large & small intestines) and the uterus

14. Simple Columnar Epithelium
Absorption cells  have microvilli on their apical surface
This increases their surface area so more of the substance can be absorbed

15. Simple Columnar Epithelium

16. Pseudostratified Columnar Epithelium
Single layer of cells with different heights; some do not reach the free surface
Nuclei are seen at different layers
Nonciliated cells are present in the male sperm-carrying ducts
Ciliated cells have cilia on the apical surface of the cells
Constantly moving, goblet cells are present and cilia sweeps the mucus away
Present in the passages of the respiratory system
Mucus from goblet cells trap dust & microorganisms; the cilia move the mucus & captured particles up and out of the airways

17. Pseudostratified Columnar Epithelium

18. Stratified Squamous Epithelium
This membrane composed of several layers of cells
Function in protection from underlying areas subjected to abrasion
Forms the external part of the skin’s epidermis (keratinized cells) and linings of the esophagus, mouth, and vagina (nonkeratinized cells)
Good at regeneration – lost cells are replaced by ones from below

19. Stratified Squamous Epithelium
Upper layers may be dead because they do not receive enough nutrients
Keratinized cells – contain a protective protein
Cells in the top layer DON’T contain nuclei
Nonkeratinized cells – do not contain the protective protein
Top layer of cells DO contain nuclei

20. Stratified Squamous Epithelium

21. Stratified Cuboidal Epithelium
Two or three layers of cuboidal cells that form the lining of a lumen
Layering of cells provides more protection than a single layer
Lines the larger ducts of the mammary glands, sweat glands, salivary glands, and pancreas
Pretty rare in the body

22. Stratified Cuboidal Epithelium

23. Stratified Columnar Epithelium
Limited distribution in the body
Found in the pharynx, male urethra, and lining some glandular ducts
*also occurs at transition areas between two other types of epithelia

24. Stratified Columnar Epithelium

25. Transitional Epithelium
Specialized to change in response to increased tension
Has several cell layers, basal cells are cuboidal, surface cells are dome shaped
Stretches to permit the distension of the urinary bladder
Forms a barrier that helps prevent the contents of the urinary tract from diffusing back into body
Lines the urinary bladder, ureters, and part of the urethra (only found in organs of the urinary system)

26. Transitional Epithelium

27. Glandular Epithelium
A gland is one or more cells that makes and secretes an aqueous fluid
Usually found within columnar and cuboidal epithelia
Contain a lot of rough ER
Secretory vesicles fuse w/ membrane & secrete fluid
Secrete lipids, proteins, steroids
Classified by:
Site of product release – endocrine or exocrine
Relative number of cells forming the gland – unicellular (goblet) or multicellular

28. Endocrine Glands Ductless glands that produce hormones
Secretions include amino acids, proteins, glycoproteins & steroids
Release secretions to surrounding systems & the hormones are transported by blood or lymphatic fluid to organs
Ex) estrogen & testosterone

29. Exocrine Glands More numerous than endocrine glands
Secrete their products onto body surfaces (skin) or into body cavities
Ex) mucous, sweat, oil & salivary glands
The only important unicellular gland is the goblet cell
Multicellular exocrine glands are composed of a duct and secretory unit

30. Connective Tissue
Found throughout the body; most abundant and widely distributed of the primary tissues
Types of connective tissue:
Loose connective tissue
Adipose tissue
Dense connective tissue
Cartilage
Bone
Blood

31. Functions of Connective Tissue
Binding & support of surrounding tissues
Protection
Insulation (adipose)
Transportation
Materials are able to go through the extracellular matrix

32. Characteristics of Connective Tissue
Connective tissues have:
Mesenchyme as their common tissue of origin
Varying degrees of vascularity
Nonliving extracellular matrix consisting of ground substances and fibers  fills spaces between cells
Collagen fibers
Elastic fibers
Reticular fibers

33. Structural Elements of Connective Tissue
Ground substance – unstructured material that fills the space between cells
Fibers – collagen, elastic, or reticular
Cells – fibroblasts, chondroblasts, osteoblasts, and hematopoietic stem cells

34. Ground Substance Interstitial (tissue) fluid
Adhesion proteins – fibronectin and laminin
Proteoglycans – glycosaminoglycans (GAGs)
Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells

35. Fibers Collagen – tough; provides high tensile strength (thickest)
Elastic – long, thin fibers that allow for stretch (medium)
Reticular – branched collagenous fibers that form delicate networks (thinnest)

36. Cells Fibroblasts – connective tissue proper Chondroblasts – cartilage
Osteoblasts – bone
Hematopoietic stem cells – blood
White blood cells, plasma cells, macrophages, and mast cells

37. Loose Connective Tissue
Also know as areolar tissue
Forms delicate, thin membranes throughout the body; widely distributed
The cells of this tissue are mainly fibroblasts; they are separated by a gel-like matrix that contains many collagenous and elastic fibers
Binds the skin to the underlying organs and fills spaces between muscles
Wraps and cushions organs

38. Loose Connective Tissue

39. Adipose Tissue
Fat
Develops when certain cells store fat in droplets within their cytoplasm and enlarge
When these cells are so numerous that they crowd other cells types they form adipose tissue
Lies beneath the skin, spaces between muscles, around the kidneys, behind the eyeballs, in abdomen, on the surface of the heart, and around certain joints
Cushions joints and the kidneys, insulates the body, stores energy in fat molecules

40. Adipose Tissue

41. Dense Connective Tissue
Consists of many closely packed, thick, collagenous fibers and a fine network of elastic fibers
It has relatively few cells  most are fibroblasts
Collagenous fibers of dense connective tissue are very strong  enables the tissue to withstand pulling forces
Often binds body parts together as parts of tendons and ligaments
Protective white layer of the eyeball & in the deeper skin layers
Tissue repair is slow because of the poor blood supply to dense connective tissue

42. Dense Connective Tissue
Attaches muscles to bone or to other muscles and bone to bone
Found in:
Tendons – attaches muscle to bone
Ligaments – attaches bone to bone
Aponeuroses – attaches muscle to muscle

43. Dense Connective Tissue

44. Cartilage Rigid connective tissue
Provides support, frameworks, and attachments, protects underlying tissues and forms structural models for many developing bones
Cartilage matrix is abundant and largely composed of collagenous fibers embedded in a gel-like ground substance
Chondrocytes  cartilage cells
Occupy small chambers called lacunae and are completely within the matrix

45. Cartilage
Cartilaginous structure is enclosed in a covering of connective tissue call perichondrium
Perichondrium contains blood vessels that provide cartilage cells with nutrients by diffusion
Cartilage does not heal quickly and chondrocytes do not divide frequently because of a lack of a direct blood supply

46. Cartilage Three types of cartilage: Hyaline cartilage
Elastic cartilage
Fibrocartilage  matrix similar to hyaline cartilage but less firm with thick collagen fibers
Provides tensile strength and absorbs compression shock
Found in the intervertebral discs, the pubic symphysis, and in discs of the knee joint

47. Hyaline Cartilage
Amorphous, firm matrix w/ imperceptible network of collagen fibers
Supports, reinforces, cushions, and resists compression
Found in embryonic skeleton, the end of long bones, nose, trachea, and larynx

48. Elastic Cartilage
Similar to hyaline cartilage but with more elastic fibers
Maintains shape and structure while allowing flexibility
Supports external ear (pinna) and the epiglottis

49. Fibrocartilage
Matrix similar to hyaline cartilage but less firm with thick collagen fibers
Provides tensile strength and absorbs compression shock
Found in the intervertebral discs, the pubic symphysis, and in discs of the knee joint

50. Bone Hard, calcified matrix with collagen fibers found in bond
Osteocytes are found in lacunae and are well vascularized
Supports, protects, and provides levers for muscular action
Stores calcium, minerals, and fat
Marrow inside bones is the site of hematopoiesis  making of red blood cells

51. Bone

52. Blood Red and white cells in a fluid matrix (plasma)
Contained within blood vessels
Functions in the transport or respiratory gases, nutrients, and wastes

53. Nervous Tissue
Branched neurons with long cellular processes and support cells
Transmits electrical signals from sensory receptors to effectors
Receptors  Brain  Effectors
Found in the brain, spinal cord, and peripheral nerves

54. Nervous Tissue

55. Muscle Tissue
Contractile – the elongated cells (muscle fibers) can shorten
As muscle tissues contract, the fibers pull at their attached ends
This moves body parts
Three types:
Skeletal
Smooth
Cardiac

56. Skeletal Muscle Tissue
Long, cylindrical, multinucleated cells with obvious striations
Multinucleated because many cells are fused together to make 1 long cell
Initiates and controls voluntary movement
Found in skeletal muscles that attach to bones or skin

57. Skeletal Muscle Tissue

58. Smooth Muscle Tissue
Sheets of spindle-shaped cells with central nuclei that have no striations  why its called smooth
Shorter than skeletal muscle
Usually can’t be stimulated to contract by conscious efforts
Propels substances along internal passageways
Ex) food down the digestive tract, constricts blood vessels, empties the urinary bladder
Found in the walls of hollow organs
Stomach, intestines, urinary bladder, uterus, blood vessels

59. Smooth Muscle Tissue

60. Cardiac Muscle Tissue Only found in the walls of the heart
Cells are striated with a single nucleus
Where cells connect to one another it is a specialized intercellular junction  intercalated disk
Cardiac muscle is controlled involuntarily
Pumps blood through the heart chambers and into blood vessels

61. Cardiac Muscle Tissue