Chapter 4. The Tissue Level of Organization

Transcription

1 Chapter 4 The Tissue Level of Organization

2 Tissues Tissues are a group of cells with a common embryonic origin that function together to carry out specialized activities.

3 Histology is the study of the microscopic anatomy of cells and tissues. Tissues Each cell type has features particular to its function.

4 Cell Junctions Tissues are formed by grouping cells together using a variety of Cell Junctions.

5 Cell Junctions Tight Junctions are found where a leakproof seal is needed between cells. They keep materials from leaking out of organs like the stomach, intestines and bladder.

6 Cell Junctions Adherens Junctions make an adhesion belt (like the belt on your pants) that keeps tissues from separating as they stretch and contract. C-adherin is a glycoprotein that forms the belt-like plaque. Epithelial cells of intestine

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8 Cell Junctions Desmosomes act as spot welds. They also use c- adherin glycoprotein (plus intermediate filaments) to hook into the cytoplasm. Epidermis, cardiac cells Skin

9 Cell Junctions Hemidesmosomes are half-welds that join cells to the basement membrane. Epithelium

10 Intracellular Junctions Gap Junctions are pores (connexons) that allow small substances like ions to pass between cells. If one of the cells gets sick or dies, these seal like a hatch to prevent damage to other cells.

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12 The 4 Basic Tissues Of all the cells in the body, they combine to make only 4 basic tissue types: Epithelial tissues Connective tissues Muscular tissues Nervous tissues

13 The 4 Basic Tissues Epithelial tissues cover body surfaces and form glands and line hollow organs, body cavities, and ducts.

14 The 4 Basic Tissues Connective tissues (C.T.) protect, support, and bind organs. Fat is a type of C.T. that stores energy. Red blood cells, white blood cells, and platelets are all C.T.

15 The 4 Basic Tissues Muscular tissues generate the physical force needed to make body structures move. They also generate heat used by the body. Nervous tissues detect changes in the body and respond by generating nerve impulses.

16 The 4 Basic Tissues Tissues of the body develop from three primary germ layers: Endoderm, Mesoderm, and Ectoderm Epithelial tissues from all three germ layers C.T. and muscle are derived from mesoderm. Nervous tissue develops from ectoderm.

17 Epithelial tissue Epithelium lines surfaces and form protective barriers. Epithelium also secretes mucous, hormones, and other substances. All epithelia have a free apical surface, lateral Surface and a basal surface.

18 Epithelial tissue The basal layer of the epithelium adheres to the basal lamina; the underlying C.T. secretes a reticular lamina. Together the basal lamina and the reticular lamina form a noncellular basement membrane on which the epithelium sits.

21 Epithelial tissue Epithelia are classified according to the shape of their cells, and the thickness or arrangement of their layers (of cells).

22 Epithelial tissue Naming epithelia according to shape Flat, wide paving stone cells Cells as tall as they are wide Cells taller than they are wide

23 Epithelial tissue Naming epithelia according to arrangement One layer. All cells in contact with basement membrane Appears to have layers, but in reality all cells go from the apex to the base Two or more layers. Only basal layer in contact with basement membrane

24 Epithelial tissue

25 Epithelial tissue Naming epithelia Three different cell shapes x three different cell arrangements = nine possibilities. Two of these are not used. Add transitional (cells that change shape), and we re back up to eight possible combinations. If different shapes are present in layers of cells, the epithelium is always named by the shape of cells in the apical layer.

26 Epithelial tissue Simple Squamous Epithelium is composed of a single layer of flat cells found: In the air sacs of lungs In the lining of blood vessels, the heart, and lymphatic vessels Kidney (Bowman s capsule) As the major part of a serous membrane simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

28 Epithelial tissue Simple Cuboidal Epithelium is composed of a single layer of cube shaped cells. It is often found lining the tubules of the kidneys and many other glands. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

30 Epithelial tissue Simple Columnar Epithelium forms a single layer of column-like cells, ± cilia, ± microvilli, ± mucous (goblet cells). Goblet cells are simple columnar cells that have differentiated to acquire the ability to secrete mucous. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

32 Epithelial tissue Pseudostratified Columnar Epithelium appears to have layers, due to nuclei which are at various depths. In reality, all cells are attached to the basement membrane in a single layer, but some do not extend to the apical surface. Ciliated tissue has goblet cells that secrete mucous. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar transitional stratified columnar

34 Epithelial tissue Stratified Squamous Epithelium has an apical surface that is made up of squamous (flat) cells. The other layers have different shapes, but the name is based on the apical layer. The many layers are ideal for protection against strong friction forces. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

37 Epithelial tissue Stratified Cuboidal Epithelium has an apical surface made up of two or more layers of cube-shaped cells. Locations include the sweat glands and part of the urethra Stratified Columnar Epithelium is very rare, and for our purposes, hardly worth mentioning. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

39 Epithelial tissue The cells of Transitional Epithelium change shape depending on the state of stretch in the tissue. The apical dome cells of the top layer (seen here in relaxation) are an identifiable feature and signify an empty bladder. In a full bladder, the cells are flattened. simple squamous pseudostratified squamous stratified squamous simple cuboidal pseudostratified cuboidal stratified cuboidal simple columnar pseudostratified columnar stratified columnar transitional

41 Epithelial tissue Although epithelia are found throughout the body, certain ones are associated with specific body locations. Stratified squamous epithelium is a prominent feature of the outer layers of the skin.

42 Epithelial tissue Simple squamous makes up epithelial membranes and lines the blood vessels. Columnar is common in the digestive tract. Pseudostratified ciliated columnar is characteristic of the upper respiratory tract. Transitional is found in the bladder. Cuboidal lines ducts and sweat glands.

43 Covering and Lining Epithelium Endothelium is a specialized simple squamous epithelium that lines the entire circulatory system from the heart to the smallest capillary it is extremely important in reducing turbulence of flow of blood.

44 Covering and Lining Epithelium Mesothelium is found in serous membranes such as the pericardium, pleura, and peritoneum. Unlike other epithelial tissue, both are derived from embryonic mesoderm (the middle layer of the 3 primary germ layers of the embryo).

45 Connective Tissue Connective Tissues are the most abundant and widely distributed tissues in the body. Functions: Bind tissues together (around muscles) Support and strengthen tissue (cartilage) Protect and insulate internal organs (adipose tissue) Compartmentalize and transport (blood) Energy reserves and immune responses (adipose tissue)

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47 Connective Tissues Collagen is the main protein of C.T. and the most abundant protein in the body, making up about 25% of total protein content. Connective tissue is highly vascular and supplied with many nerves.

48 Connective Tissues Two basic elements: Cells Extracellular matrix Protein fibers Ground substance: Hyaluronic acid Chondroitinsulfate

49 Cells Of Connective Tissues Fibroblasts are the most numerous cell of connective tissues. These cells secrete protein fibers (collagen, elastin, & reticular fibers) and the ground substance

50 Cells of Connective Tissues Other C.T. cells: Chondrocytes make the various cartilaginous C.T. Adipocytes store triglycerides. Osteocytes make bone. White blood cells are part of the blood.

51 Connective Tissues White blood cells (WBCs) also found in CT: Macrophages are the big eaters that swallow and destroy invaders or debris. They can be fixed or wandering. Neutrophils are also macrophages ( small eaters ) that are numerous in the blood. Mast cells and Eosinophils play an important role in inflammation. Lymphocytes secrete antibody proteins and attack invaders.

52 Connective Tissues Ground susbtance: supports cells, stores water, provides medium for exchange of substances. Composed by GAGs (glycosaminoglycans): chondrotin sulfate, dermatan sulfate, hyaluronic acid Copyright John Wiley & Sons, Inc. All rights reserved.

53 Connective Tissues C.T. cells secrete 3 common fibers: Collagen fibers Elastin fibers Reticular fibers

54 Connective Tissue Classification Embryonic connective tissue Mesenchyme Mucous connective tissue

55 Embryonic Connective Tissues There are 2 Embryonic Connective Tissues: Mesenchyme gives rise to all other connective tissues.

56 Mucous C.T. (Wharton's Jelly) is a gelatinous substance within the umbilical cord and is a rich source of stem cells.

57 Connective Tissue Classification Mature connective tissue Loose connective tissue Areolar connective tissue Adipose tissue Reticular connective tissue Dense connective tissue Dense regular connective tissue Dense irregular connective tissue Elastic connective tissue Cartilage Hyaline cartilage Fibrocartilage Elastic cartilage Bone Liquid Blood tissue Lymph Copyright John Wiley & Sons, Inc. All rights reserved.

58 Mature Connective Tissues Loose Connective Tissues Areolar Connective Tissue is the most widely distributed in the body. It contains several types of cells and all three fiber types. It is used to attach skin and underlying tissues, and as a packing between glands, muscles, and nerves.

60 Mature Connective Tissues Loose Connective Tissues Adipose tissue is located in the subcutaneous layer deep to the skin and around organs and joints. It reduces heat loss and serves as padding and as an energy source.

62 Mature Connective Tissues Loose Connective Tissues Reticular connective tissue is a network of interlacing reticular fibers and cells. It forms a scaffolding used by cells of lymphoid tissues such as the spleen and lymph nodes.

64 Mature Connective Tissues Dense Connective Tissues Dense Irregular Connective Tissue consists predominantly of fibroblasts and collagen fibers randomly arranged. It provides strength when forces are pulling from many different directions.

66 Mature Connective Tissues Dense Connective Tissues Dense regular Connective Tissue comprise tendons, ligaments, and other strong attachments where the need for strength along one axis is mandatory (a muscle pulling on a bone).

68 Mature Connective Tissues Dense Connective Tissues Elastic Connective Tissue consists predominantly of fibroblasts and freely branching elastic fibers. It allows stretching of certain tissues like the elastic arteries (the aorta).

70 Mature Connective Tissues Cartilage is a tissue with poor blood supply that grows slowly. When injured or inflamed, repair is slow. Hyaline cartilage is the most abundant type of cartilage; it covers the ends of long bones and parts of the ribs, nose, trachea, bronchi, and larynx. It provides a smooth surface for joint movement.

72 Mature Connective Tissues Cartilage Fibrocartilage, with its thick bundles of collagen fibers, is a very strong, tough cartilage. Fibrocartilage discs in the intervertebral spaces and the knee joints support the huge loads up and down the long axis of the body.

74 Mature Connective Tissues Cartilage Elastic cartilage consists of chondrocytes located in a threadlike network of elastic fibers. It makes up the malleable part of the external ear and the epiglottis.

76 Mature Connective Tissues Bone is a connective tissue with a calcified intracellular matrix. The chondrocytes of cartilage are capable of turning into the osteocytes that make up bone tissue.

78 Mature Connective Tissues Blood and lymph are atypical liquid connective tissues.

79 Muscle and Nerve Tissues

80 Epithelial Membranes Epithelial membranes are the simplest organs in the body, constructed of only epithelium and a little bit of connective tissue.

81 Epithelial Membranes Epithelial membranes = epithelium + connective tissue Mucous membranes Serous membranes Cutaneous membrane = skin

83 Epithelial Membranes Serous membranes line some internal surfaces: Parietal layer next to body wall Serous fluid between layers Visceral layer next to organ

84 Epithelial Membranes

85 Synovial Membranes Synovial membranes enclose certain joints and are made of connective tissue only.

86 Glands Epithelial glands are another example of simple organs Glands that secrete their contents directly into the blood are called endocrine glands. Glands that secrete their contents into a lumen or duct are called exocrine glands.

87 Exocrine Glands Exocrine glands secrete substances through ducts to the surface of the skin or into the lumen of a hollow organ. Secretions of the exocrine gland include mucus, sweat, oil, earwax, saliva, and digestive enzymes. Examples of exocrine glands are sudoriferous (sweat) glands.

88 Exocrine Glands The two criteria for categorizing multicellular glands according to structure: Whether the ducts are branched or unbranched In a simple gland the duct does not branch. In a compound gland the duct branches. and the shape of the secretory portion of the gland Tubular glands have tubular secretory parts. Acinar glands have rounded secretory parts. Tubuloacinar glands have features of both.

89 Exocrine Glands unbranched duct (simple) branched duct (compound)

90 Exocrine Glands The functional classification is based on the manner in which the gland secretes its product from inside the cell to the outside environment. Merocrine Apocrine Holocrine

91 Exocrine Glands Merocrine secretion is the most common manner of secretion. The gland releases its product by exocytosis and no part of the gland is lost or damaged.

92 Exocrine Glands Apocrine glands bud their secretions off through the plasma membrane, producing membrane-bound vesicles in the lumen of the gland. The end of the cell breaks off by decapitation.

93 Exocrine Glands Holocrine secretions are produced by rupture of the plasma membrane, releasing the entire cellular contents into the lumen and killing the cell (cells are replaced by rapid division of stem cells.) The sebaceous gland is an example of a holocrine gland, because its secretion (sebum) is released with remnants of dead cells.

94 Tissue Repair A convenient way to refer to certain cells when discussing a tissue is Parenchyma or Stroma. The parenchymal cells of an organ consist of that tissue which conducts the specific function of the organ. Cells of the stroma are the supporting cells like connective tissue, and contains blood vessels, nerves. For example: The parenchyma of the heart is cardiac muscle cells. The nerves, intrinsic blood vessels, and connective tissue of the heart comprise the stroma.

95 Tissue Repair When tissue damage is extensive, return to homeostasis depends on active repair of both parenchymal cells and stroma. Fibroblasts divide rapidly. New collagen fibers are manufactured. New blood capillaries supply materials for healing. All of these processes create an actively growing connective tissue called granulation tissue.

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98 Aging and Tissues Tissue heals faster in young adults. Surgery of a fetus normally leaves no scars. Young tissues have a better nutritional state, blood supply, and higher metabolic rate. Extracellular components also change with age. Changes in the body s use of glucose, collagen, and elastic fibers contribute to the aging process.