1. Tissue

2. Definition
A tissue is a group of usually similar cells, which together with their intercellular substance, perform a particular function.
The study of tissue is Histology.
Cells, cytoskeletal filaments and the extracellular matrix are major components of tissue

3. The Extracellular Matrix
Secreted by cells
Provides supportive tissue their strength
In some cases, the ECM provides cells a medium by which cells can be bound together
However, cells can be connected directly to each other.
Details on cell junctions to come

4. Animal Tissue Animals are predators and must be strong and agile
Means that tissue must possess characteristics of capable of rapid movement and the cells that make up the tissue must be able to generate and transmit forces and change shape quickly

5. Animal Tissue II Epithelial tissue Connective Tissues Muscular Tissue
Nervous Tissue

6. Animal Tissue
Connective tissue

7. Connective Tissue I Characteristics
Extremely varied
Tough and flexible
Tendons
Dermis of the skin
Hard and dense
Bone
Resilient and shock-absorbing
Cartilage
Soft and transparent
Jelly that fills interior of the eye

8. Connective Tissue II Functions
Supporting function
Cartilage
Bone
Transport function
Blood

9. Connective Tissue III
Bulk of this tissue is composed of extracellular matrix
Tensile strength provided by the fibrous protein collagen

10. Connective Tissue IV Collagen
There are 20 different variations of the protein
Chief proteins in bone, tendon and skin
Make up 25% of the total protein mass in a mammal
More than any other type of protein
Collagen is long, stiff and a triple stranded helical structure
Collagen fibrils
10-300nm in diameter

11. Connective Tissue V Collagen
Homework Question
How does procollagen and the extracellular enzyme collagenase relate to the formation of collagen?
What is the result of a genetic disorder that results in the deficit of the enzyme collagenase?
Procollagen to collagen-collagen fibrils do not assemble correctly
Hyperextensible skin

12. Connective Tissue VI Connection to and Movement of Cells Within the ECM
Cells move by pulling on the matrix and crawl over it
Hence cells must attach to the matrix
Actin filament (cell) (binds)Adaptor protein (cell) Integrin (plasma membrane) Fibronectin (ECM) Collagen (ECM)
Integrin—receptor protein found in the plasma membrane

14. Muscular tissue

15. Muscular Tissue All muscle cells can contract
Voluntary Skeletal Muscle
The main type found in mammals
Composed of
Myofibrils
Made up of myofilaments
Actin
Myosin
Responsible for striped appearance

17. Nervous tissue

18. Nervous Tissue
Has highly developed properties of irritability and conductivity.
Composed of packed nerve cells known as neurons.

19. Epithelial tissue

20. Epithelial Tissue Acts as a protective barrier
There are more than 200 visible cell types in the body of a vertebrate
Acts as a protective barrier
May have complex biochemical functions and secrete specialized products
Hormones
Milk
Tears
Absorb nutrients
Lining of the gut
Detect signals
Photoreceptors of the eye
Auditory hair cells of the ear

21. Epithelial Tissue II Form
Cells joined together, side to side, to form multicelluar sheets
Thick sheets (many cells)
Stratified
Epidermis covering of the skin
One cell thick
Simple
Lining of the gut

22. Epithelial Tissue III Form
Cells may be tall
Columnar
Cells may be cubed shape
Cuboidal
Cells may be “flat”
Squamous

23. Epithelial Tissue IV
Since epithelial tissue are in the form of sheets, they have two sides (faces)
Apical surface
Free and exposed to the air or to a watery fluid
Basal surface
Rests on some other tissue
Usually connective tissue
Basal lamina
The basal lamina (often confused with the basement membrane, and sometimes used inconsistently in the literature, see below) is a layer on which epithelium sits and which is secreted by the epithelial cells.

24. Epithelial Tissue V Columnar epithelium
Tall narrow cells often with cilia
Used in transporting mucus and other particles
Found in
Nasal cavities
Trachea
Oviducts
Ventricles of the brain

25. Epithelial Tissue VI Squamous epithelium Called “pavement epithelium”
Flattened single layer of thin nucleated cells
Found where rapid diffusion takes place
Bowman’s capsule
Alveoli
Endothlium

26. Epithelial Tissue VII Compound (Stratified Epithelium)
Many layers of cells
Ones nearest to the basement are normally flattened and dead
Impregnated with keratin
Found where there is considerable mechanical stress
Epidermis of skin
Esophagus
Anal cavity
Vagina

27. Epithelial Sheets And Cell to cell connections

28. Introduction
Epithelial cell junctions can be classified according to their function
Prevent leakage of molecules
Provide strong mechanical attachments
Provide a special type of intimate chemical communication
In most epithelia, all types of junctions are present together

29. Tight Junctions Sealing function in invertebrates
Seal neighboring cells together so that water-soluble molecules cannot easily leak between the cells
Make the epithelium leak proof
Separate the apical and basal surfaces

30. Desmosome
Considered as a “spot weld,” anchors intermediate filaments in one cell to those in a neighboring cell
Specifically keratins, an intermediate filament, found in epithelia
Anchorage is mediated by integrin proteins in the basal plasma membrane of epithelial cells

31. Gap Junction Allows passage of small water-soluble ions and molecules
Found in most epithelial cells and many other types of tissue
Identical plasma membranes found in opposite cells
Connexons
Gap junctions, found between heart muscle cells, provide the electrical coupling that allows electrical waves of excitation to spread through the tissue, triggering coordinated contraction of the cells.

32. Plant Tissue

33. Plant Tissue Plants are sedentary in comparison to animals
Tissue is more, or less, rigid
Cells, when taken into isolation, are weak and fragile
The strength of plants rise from the cell walls
Cell wall
Type of extracellular matrix, that the cell secrete around itself, allows “wood” to be thick and hard or thin and flexible in a leaf

35. Cell to Cell Connection Plasmodesmata
Found in plant tissue
Cytoplasms of adjacent plant cells are connected via minute communicating channels called plasmodesmata
Lined with plasma membrane common to the two connected cells.
Contains a fine tubular structure, desmotubule, derived from the smooth endoplasmic reticulum
Allows restricted range of ions and small molecules to pass
Similar to gap junctions found in animal tissue

36. Plasmodesmata

37. Plant Tissue Three Tissue Systems Dermal Tissue Vascular Tissue
Plant’s protective covering in contact with the environment
Facilitates water and ion uptake in roots
Regulates gas exchange in leaves and stems
Vascular Tissue
Xylem & phloem
Conducts water and solutes between organs
Provides structural support
Ground Tissue
Packing and supportive tissue
Food manufacturing and storage

39. Dermal Tissue Epidermis
Primary outer protective, usually of one layer of cells, covering of the plant
Cells of epidermis have thick primary cell walls and are covered by a special cuticle.
Modified cells, of the epidermis, form hairs of various kinds and stomata

40. Dermal Tissue II Stomata Openings in the epidermis
Regulate gas exchange in the plant
Formed by two specialized epidermal cells
Guard cells
Regulate the diameter of the pore
Distributed in species-specific pattern within each epidermis

41. Dermal Tissue III Hairs Appendages derived from epidermal cells
Trichomes
Appendages derived from epidermal cells
Function in protection, absorption and secretion
Cotton seed
Single hair cells developing the epidermis if cotton seed
Walls will be secondarily thickened with cellulose to form cotton fibers
Root hairs are used to take up water and ions from the soil

42. Trichomes

43. Ground Tissue Three main types of cells Parenchyma Collenchyma
Sclerenchyma

44. Ground Tissue Cell Types

45. Parenchyma Cells
Unspecialized cells, with a variety of functions, that are a major component of ground tissue.
Apical and lateral meristematic cells of shoots and roots provide new cells required for growth
Storage
Food production and storage occur in the photosynthetic cells of the leaf
Mesophyll cells
Storage parenchyma cells form the bulk of most fruits and vegetables
Present in vascular tissues
Tissue used in the movement of substances through the plant

46. Collenchyma Cells
Similar to parenchyma cells except that the cell walls are thicker and are usually elongated and packed into ropelike fibers
Primary cell wall is thickened with cellulose and pectin but not lignin
Capable of stretching and provide mechanical support in the ground system of the elongating regions of the plant
Common in the subepidermal regions of stems
Function in supporting younger cells where plasticity is necessary to allow for changing growth requirements
Pits are present in the cell walls

47. Collenchyma Cells

48. Sclerenchyma Cells Strengthening and supporting functions
Usually dead cells with thick lignified secondary cell walls
Forms supporting tissue with a secondary cell wall, composed of lignin, deposited on the primary cell wall of cellulose
Two basic types
Sclerids
Short and unbranched cells found in seed coats and fruit
Fibres
Form long bundles
Found often in the vascular bundles of dicotyledons or around the vascular bundles of monocotyledons
Jute
Hemp
Flax

49. Xylem
Primary xylem is doemed from the embryo and the resultant meristems
Secondary xylem, which develops later, is formed during secondary thickening
Four main elements
Vessels
Cells have more than one perforation at each end so that water can move easily from cell to cell
Tracheids
Cells have no open ends and the pits occur in pairs so that the water can pass easily through the thin pit membrane

50. Xylem II Fibres Parenchyma
Long cells whose secondary walls are commonly lignified.
Pits frequent
Used for support
Parenchyma

51. Phloem Primary phloem develops from the procambium
Secondary phloem develops from the vascular cambium
Four main elements
Sieve tubes
Highly specialized phloem cells
Companion cells
Form from sieve tubes early in their development
Contains a nucleus where the sieve tube does not
Walls between two are thin and densely pitted
Sclerenchyma
Parenchyma