Tissues

1. Anatomy Tissues

2. Tissues-Four Basic Types • Epithelial Tissue • Connective Tissue • Muscular Tissue • Nervous Tissue

3. Epithelium Characteristics • Epithelial tissue- covers surfaces with an uninterrupted layer of cells.   • Epithelial cells- are attached to one another.   • Intercellular spaces in epithelium are small.     • Epithelial cells- are separated from the underlying tissue by a basement membrane.  • Epithelium- is named according to the number of cell layers and the shape of the cells. 

4. Epithelium Cell Layers (stratification) • Simple: There is a single layer of cells. • Stratified: More than one layer of cells. The superficial layer is used to classify the layer. Only one layer touches the basement membrane. Stratified cells can usually withstand large amounts of stress. • Pseudostratified Columnar: There is only a single layer of cells, but the position of the nuclei gives the impression that it is stratified. All cells are in contact with the basement membrane, but all do not reach the free surface.

5. EpitheliumCell Shapes • Squamous- Flat cells (like pancakes) • Cuboidal- Cells that are about as wide as they are tall (cube-like) • Columnar- Cells that are tall (columns)

6. Epithelium Simple Squamous Model (surface view)

7. Epithelium Simple Squamous(surface view) Location • lungs (alveoli) • capillary endothelium (inner lining) • lining of pleural cavity, the pericardium, and the peritoneum • Bowman's capsule (Kidney)

8. Epithelium Epithelium Stratified Squamous Location • From lining of the esophagus

9. Epithelium Stratified Squamous (Thin Skin) Location • The stratified squamous epithelium of thin skin has thin layers of keratin on the upper surface. Note that the epithelium rests on dense irregular connective tissue below (light pink).

10. Epithelium Simple Cuboidal • follicle of thyroid gland • collecting ducts of kidney • salivary glands • pancreas

11. Epithelium Stratified Cuboidal Location • ducts of sweat glands

12. Epithelium Simple Columnar Location • gall bladder • surface epithelium of stomach • Uterine glands • small intestine

13. Epithelium Stratified Columnar Location • large excretory duct of salivary glands • parotid • submandibular • sublingual

14. Epithelium Pseudostratified Location • Our large airways are lined by ciliated Pseudo- stratified epithelium. • The cilia beat towards the throat. They propel a thin layer of mucus, so that you can cough it up when you "clear your throat.“

15. Epithelium Transitional (Changes from an empty relaxed urinary bladder to a stretched full bladder) Location • urinary bladder Empty Bladder (relaxed) Full Bladder (distended)

16. Connective Tissue • Connective tissue consists of cells separated by varying amounts of extracellular substance. • In connective tissues cells typically account for only a small fraction of the tissue volume unlike epithelial tissue. • The extracellular substance consists of fibers which are embedded in ground substance containing tissue fluid. • Fibers in connective tissue can be divided into three types: collagen fibers, elastic fibers and reticular fibers. • Collagen fibers are the most abundant protein fibers in the body. • Elastic fibers are made of elastin and are "stretchable.“ • Reticular fibers are very fine collagen fibers that join connective tissues to other tissues. • The principle roles of connective tissue are to bind or strengthen organs or other tissues. It also functions inside the body to divide and compartmentalize other tissue structures.

17. Connective Tissue Types • Areolar (loose connective tissue) holds organs and epithelia in place. • Adipose tissue contains adipocytes, used for cushioning, thermal insulation, lubrication (primarily in the pericardium) and energy storage. [fat] • Dense connective tissue (or, less commonly, fibrous connective tissue) forms ligaments and tendons Its densely packed collagen fibers have great tensile strength. • Reticular connective tissue is a network of reticular fibers (fine collagen, type III) that form a soft skeleton to support the lymphoid organs (lymph nodes, bone marrow, and spleen.) • Blood functions in transport. Its extracellular matrix is blood plasma, which transports dissolved nutrients, hormones, and carbon dioxide in the form of bicarbonate. The main cellular component is red blood cells. • Bone makes up virtually the entire skeleton. • Cartilage is found primarily in joints, where it provides cushioning. The extracellular matrix of cartilage is composed primarily of collagen.

18. Loose Connective Tissue • As the name implies, loose connective tissue consists of a loosely woven mix of fibers, cells, and ground substance.   • Areolar, a more technical name used for this tissue type means "spaces".   • Loose connective tissue therefore possesses randomly arranged protein fibers with abundant intercellular spaces.   • Scattered within the spaces are 7 cell types.

19. Loose Connective Tissue • Macrophages arise from precursor cells called monocytes. • They are actively mobile and leave the blood stream to enter connective tissues, where they differentiate into macrophages. • Macrophages change their appearance depending on the demand for phagocytotic activity. • Mast cells are - like macrophages, lymphocytes and eosinophils - in demand when something goes wrong in the connective tissue. • Mast cells facilitate an immune response to antigens which triggered the release of histamine and heparin. • Lymphocytes play an important and integral role in the body's defenses. • Fibrocytes are the most common cell type in connective tissues. • Fibroblasts contain large amounts of the organelles which are necessary for the synthesis and excretion of proteins needed to repair the tissue damage.

20. Loose Connective Tissue • The loose CT in the duodenum is a "space filler" that provides the flexibility the GI tract needs. • Many of the nuclei present are probably fibroblasts, but other cell types common in loose CT include plasma cells, mast cells, and lymphocytes.

21. Loose Connective Tissue • Two types of adipose cells are found in fat tissues, white and brown adipocytes.   • These adipose cell types vary in their ability to mobilize energy from stored fat. • Brown fat cells are smaller and more efficient at converting fat into available energy.   • Brown fat is more typical in infants, being replaced gradually by white fat as we age.   • In both cell types fat droplets enlarge to push nuclei and cytoplasm to the periphery.

22. Loose Connective Tissue • Although present as the supportive tissue of lymph nodes, glands, organs, and bone marrow, reticular connective tissue is not that obvious.   • Small, branching, collagen fibers that form the reticular connective tissue are usually hidden from view by the numerous lymphatic, epithelial, or bone marrow cells anchored to them.   • The stroma, or supporting network of reticular fibers is best seen with special stains.

23. Loose Connective Tissue • Loose connective tissues of membranes are important sites of inflammation due to mast cells. • Mast cells release histamine, heparin(an anticoagulant), and other vasoactive agents.   • Vascular effects of histamine are important initiators of inflammation. • These include vasodilation in vessels and increased permeability in capillaries. • The visible signs of inflammation are explained by keeping histamine's vascular effects in mind.

24. Loose Connective Tissue

25. Dense Regular Connective Tissue Tendon Ligament

26. Supportive Connective Tissue- Cartilage • Cartilage is a flexible but strong supportive connective tissue.   • Unlike bone and all other connective tissue types, cartilage is avascular,  lacking blood vessels. • Three varieties of cartilage: hyaline; elastic; and fibrocartilage

27. Supportive Connective Tissue

28. Supportive Connective Tissue- Cartilage Fibrocartilage Hyaline Elastic

29. Supportive Connective Tissue- Bone • Bone is the major structural and supportive connective tissue of the body.   • The matrix of bone contains abundant collagen fibers and these impart strength, some flex, and resistance to twisting or torsional forces.   • Surrounding these "reinforcing rods" of collagen is a cement-like ground substance called hydroxyapatite.   • This mineral complex of calcium phosphate salts makes bone highly resistant to compression forces. • Together, collagen fibers and hydroxyapatite make bone one of the strongest and lightest materials known.

30. Supportive Connective Tissue- Bone

31. Supportive Connective Tissue- Cancellous Bone • During bone formation, the first bone to form is always cancellous. • Have no Haversian Systems or Osteons • Open spaces between trabeculae of cancellous bone are typically occupied by red bone marrow.   • Red Marrow is the source for all "formed elements" of the blood. • Found at the end of long bones and in the middle of flat bones Cancellous (Spongy) Bone trabeculae

32. Supportive Connective Tissue- Bone • Compact bone is a highly structured, dense type of bone found where maximum strength is required. • There are many lacunae(the small dark spots) where mature bone cells or osteocytesare found. •  Bone forming cells or osteoblastsare never found in lacunae but rather along the edges of bone where new lamellae form.  When an osteoblast is completely surrounded by the forming hydroxyapatite, it becomes an osteocyte.   • A third type of bone cell to remember is the osteoclast, also found along the edges of bone.   • Osteoclasts are active where bone or calcified cartilage is being resorbed and restructured. Compact Bone

33. Bone Tissue Cancellous (Spongy) Bone Compact bone Cancellous (Spongy) Bone

34. Muscle Tissue

35. Skeletal Muscle Tissue • Skeletal muscle is a type of striatedmuscle, usually attached to the skeleton. • Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction. • They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes. • Muscle cells (also called fibers) have an elongated, cylindricalshape, and are multinucleated.

36. Smooth Muscle Tissue • Smooth muscle is a type of non-striatedmuscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the ciliary muscle and iris of the eye. • Smooth muscle fibers are spindle shaped, and like all muscle, can contract and relax.

37. Cardiac Muscle Tissue • Cardiac muscle is the muscle that makes up the wall of the heart. • Cardiac muscle is similar to skeletal muscle in that it is striated and similar to smooth muscle in that the nuclei are centrally located and many cells are required to span the length of the muscle. • It differs from both skeletal muscle and smooth muscle in that its cells branch and are joined to one another via intercalated discs.

38. Nervous Tissue • Neurons (also known as neurones and nerve cells) are electrically excitable cells in the nervous system that process and transmit information. • Neurons are the core components of the brain, spinal cord and peripheral nerves. • Neurons are typically composed of a soma, or cell body, a dendritic tree and an axon.