Histology. Study of body tissues

Transcription

1 Histology Study of body tissues

2 2

3 Introduction to Body Tissues 1. Composed of specialized cells of similar structure and perform a common function 2. Four major types (4 Cs) a. Epithelial - Cover b. Connective - Connect c. Muscular - Contract d. Nervous - Communicate 3. Organs composed of all four types of tissue 3

4 4.1 Epithelial Tissue (Cover) 4

5 A. General characteristics 1. Cells are tightly packed 2. Protects external and internal body surfaces 3. Also secretes and absorbs substances 4. Epithelial cells readily divide to replace lost or damaged cells 5. Cells are avascular (lack a blood supply) 6. Has a free surface and a basement membrane 7. Classified by cell shape and the number of cell layers 5

6 B. Classification of Epithelial Tissue 1. Number of cell layers a. Simple epithelial tissue: one b. Stratified epithelial tissue: two or more 2. Shape of the cells a. Squamous epithelium = flattened b. Cuboidal epithelium = cube-shaped c. Columnar epithelium = elongated 3. Two additional special tissues 6

7 C. Squamous epithelium 1. Simple squamous epithelium a. Composed of a single layer of flattened cells b. Found in areas where simple diffusion occurs alveoli, capillaries 7

8 Simple squamous epithelium 8

9 Squamous epithelium, cont 2. Stratified squamous epithelium a. many cell layers b. deeper cells may be cuboidal or columnar c. outer cells are flattened and squamousshaped d. Found in the outer portion of the skin and in body orifices 9

10 Stratified squamous epithelium 10

11 D. Cuboidal epithelium 1. Simple cuboidal epithelium a. Single layer of cube-shaped cells attached to a basement membrane b. Found in glands, function is secretion c. Lots ofmitochondria to produce ATP d. Free surface may have microvilli e. Covers the ovaries f. Lines most of the kidney tubules where it absorbs and secretes substances 11

12 Cuboidal epithelium, cont 2. Stratified cuboidal epithelium a. Often only two layers b. Mostly found lining the larger ducts of certain glands 12

13 Simple Cuboidal epithelium 13

14 E. Columnar epithelium 1. Simple columnar epithelium a. Cells longer than they are wide b. Modified for particular functions c. Some cells are goblet cells that secrete mucus or have microvilli d. Lines digestive organs and the uterine tubes 2. Stratified columnar epithelium a. Not very common b. Located in parts of the pharynx and in the male urethra 14

15 Simple columnar epithelium 15

16 F. Pseudostratified columnar epithelium 1. Appears to have more than one layer of cells, but only has one true layer 2. Each cell touches the basement membrane 3. Pseudostratified ciliated columnar epithelium lines parts of the reproductive system and air passageways of the respiratory system 4. Contains goblet cells and cilia 16

17 Pseudostratified ciliated columnar epithelium 17

18 G. Transitional epithelium 1. Changes in response to tension from cuboidal to squamous cells 2. Located in urinary bladder, the ureters, and part of the urethra 3. Allows these organs to stretch 4. Cells are physically able to slide in relation to one another 18

19 4.2 Connective Tissue (Connect) 20

20 A. General characteristics 1. Binds structures together, provides support and protection, fills spaces, produces blood cells, and stores fat 2. Cells are separated by extracellular matrix (nonliving) 21

21 B. Fibrous Connective Tissue 1. Loose (areolar) connective tissue a. Cells of this tissue are mainly fibroblasts b. Contains many collagen and elastin fibers in a fine web like arrangement c. Adipose tissue is a type of loose connective tissue in which the cells enlarge and store fat 22

22 Loose (areolar) connective tissue 23

23 Adipose Tissue 24

24 2. Dense Connective Tissue a. Has thick bundles of collagen fibers b. In dense regular connective tissue the bundles are parallel (as in tendons, ligaments, and aponeuroses) c. In dense irregular connective tissue the bundles run in different directions (in the dermis and joint capsules) d. In reticular connective tissue the cells are reticular cells and the matrix contains only reticular fibers (also called lymphatic tissue) (forms a mesh or web) 25

25 Dense regular connective tissue 26

26 Dense irregular connective tissue 27

27 C. Connective tissue - Cartilage 1. Cells called chondrocytes are found in small chambers called lacunae; chondroblasts produce the cartilage tissue 2. Because it is avascular, it heals slowly 3. Hyaline cartilage a. Most common type b. Contains only collagen fibers c. Found in the nose, ends of long bones and ribs, in the supporting rings of the trachea, and the embryonic skeleton 28

28 Cartilage, cont 4. Elastic cartilage a. Matrix contains many elastic fibers; also contains collagen fibers; more flexible than hyaline cartilage b. Found in the outer ear 5. Fibrocartilage a. Matrix contains strong collagen fibers b. Absorbs shock c. Found between the vertebrae and in the knee joint 29

29 Three types of cartilage 30

30 D. Connective tissue - bone 1. Extremely hard matrix composed of mineral salts deposited around collagen fibers 2. Bones cells osteoblasts produce the organic part of bone, then become osteocytes 3. Compact bone Haversian systems 4. Spongy bone trabeculae and bone marrow 31

31 Bone tissue 32

32 E. Connective Tissue - Blood 1. Composed of formed elements (cells) a. Red blood cells (erythrocytes) - carry oxygen b. White blood cells (leukocytes) fight infection c. Platelets (thrombocytes) blood clotting 2. Liquid matrix is called plasma and is not formed by the tissue cells 33

33 Blood 34

34 Classification of Connective Tissue 35

35 4.3 Muscular Tissue (Contract) 36

36 A. General characteristics 1. Cells are called fibers because they are long 2. Cells contain actin and myosin which are contractile proteins 37

37 B. Skeletal Muscle Tissue 1. Voluntary muscle 2. Attached to bones of the skeleton by tendons 3. Contraction causes movement of body parts 4. Have a cylindrical shape and are long 5. Muscle fibers (cells) have multiple, peripherally located nuclei 6. Muscle fibers appear striated due to the placement of actin and myosin filaments in the fiber 38

38 Skeletal Muscle 39

39 C. Smooth Muscle Tissue 1. Visceral muscle found in the walls of hollow viscera (organs) 2. Spindle-shaped cells with one central nucleus 3. Under involuntary control 4. No striations 5. Contract rhythmically, on its own, but can be modified by the nervous system 40

40 Smooth Muscle 41

41 D. Cardiac Muscle Tissue 1. Found only in the walls of the heart 2. Pumps blood 3. Cardiac muscle cells have striations, like skeletal muscle 4. Is involuntary, like smooth muscle 5. Cardiac muscle cells have a single, centrally located nucleus and are branched 6. Cardiac muscle cells are bound to one another by intercalated disks 42

42 Cardiac Muscle 43

43 Classification of Muscular Tissue 44

44 4.4 Nervous Tissue (Communicate) 45

45 A. Neurons 1. Found in the brain and spinal cord 2. Neurons (nervous tissue cells) generate and conduct nerve signals. 3. A neuron has three parts: a. Dendrite receives an impulse b. Cell body contains the nucleus c. Axon conducts nerve impulses 4. Long axons are called fibers and form tracts in the brain and spinal cord and nerves in the body 46

46 Nervous Tissue 47

47 B. Neuroglia 1. More numerous nervous tissue cells 2. Support and nourish neurons, but do not conduct an impulse 3. Types of neuroglia found in the brain: a. Microglia engulf bacteria and cellular debris b. Astrocytes produce glial-derived growth factor c. Oligodendrocytes form the myelin sheath d. Ependymal cells line the ventricles 4. Schwann cells are neuroglia located outside the brain or spinal cord that produce the myelin sheath around nerves 48

48 4.5 Extracellular Junctions, Glands, and Membranes 49

49 A. Extracellular Junctions 1. Junctions between cells help cells function as a tissue 2. Types of cell junctions: a. Tight junction plasma membrane proteins join, forming an impermeable barrier b. Gap junction plasma membrane channels join, allowing substances to pass between the two cells c. Adhesion junction (desmosome) adjacent plasma membranes held together by extracellular filaments 50

50 Extracellular Junctions 51

51 B. Glands 1. Consists of one or more cells that produce and secrete a product 2. Most are composed of epithelium 3. Exocrine glands secrete their product onto the outer surface or into a cavity a. Ex: Goblet cells and sweat glands 4. Endocrine glands are ductless and secrete their product internally to be transported by the bloodstream a. Ex: pituitary and thyroid glands 52

52 Multicellular Exocrine Glands 53

53 C. Membranes 1. Mucous membranes a. Line interior walls of the organs and tubes that open to the outside of the body digestive, respiratory, urinary, and reproductive systems b. Consist of epithelium overlying a layer of loose connective tissue c. Epithelium contains goblet cells that secrete mucus 54

54 2. Serous Membranes a. Parietal membranes line the thoracic and abdominopelvic cavities b. Visceral membranes cover internal organs c. Consist of a layer of simple squamous epithelium overlying a layer of loose connective tissue d. Secrete serous fluid that lubricates the membranes e. Pleura serous membranes in the thorax 1) Parietal pleura lines thoracic wall 2) Visceral pleura covers the surface of the lungs 55

55 Serous membranes, cont f. Pericardium covers the heart (also double) g. Peritoneum serous membranes within the abdomen 1) Parietal peritoneum lines the abdominopelvic wall 2) Visceral peritoneum covers the organs in the abdominopelvic cavity 56

56 Membranes, cont 3. Synovial membranes a. Line freely movable joint cavities b. Composed of connective tissue c. Secrete synovial fluid that lubricates the ends of bones 4. Meninges a. Found within the posterior cavity b. Composed entirely of connective tissue c. Protective covering for the brain and spinal cord 57

57 Membranes, cont 5. Cutaneous membrane (skin) a. Forms the outer covering of the body b. Consists of an outer portion of keratinized stratified squamous epithelium attached to a thick layer of dense connective tissue 58