Tissues

1. Tissues Chapter 5 http://asweknowit.net/images_edu/dwa5%20tissues.jpg

2. 4 Types of Tissues All tissues can be classified into four major categories based on structure and function: • Epithelial: Covers and protect body surfaces, lines body cavities, moves substances in and out of blood (secretion, excretion & absorption), form glands • Connective: support, connection, transport, protection • Muscle: moves the body & its parts; specialized for contractility • Nervous: provides communication between body parts and coordinates body functions

3. Embryonic Development • Zygote becomes a blastocyst through mitotic division • Cells of the blastocyst regroup into primary germ layers • Endoderm, mesoderm, ectoderm • Gastrulation • Histogenesis

5. Epithelial Tissue Subdivided into 2 types: • Membranous • Covers the body & some of its parts • Lines body cavities (pleural, pericardial, peritoneal), blood vessels, respiratory, digestive and genitourinary tracts • Glandular • Form the secretion units of the endocrine & exocrine glands

6. Epithelial Tissue Functions of epithelial tissues: • Protection • Ex: skin protects body from injury & disease-causing micro-organisms • Sensory • Epithelial structures that specialize in sensory functions found in skin, nose, eye, ear • Secretion • Glandular epithelium secrete hormones, digestive juices & sweat • Absorption • Ex: gut absorbs nutrients; exchange of respiratory gases • Excretion • Ex: kidney tubules concentrate & excrete urine and other waste products

7. Epithelial Tissue • Basement membrane • Thin, noncellular layer of adhesive • Connects epithelial tissue and underlying connective tissue • Avascular • “without” vascular • Epithelial cells do not have blood vessels • Oxygen & nutrients diffuse from capillaries through connective tissue & basement membrane to epithelial cells

8. Classification of Membranous Epithelial Tissue • Cell Shape • Squamous: flat, plate-like • Cuboidal: cube-shaped; larger cytoplasm • Columnar: narrow and cylinder-shaped • Pseudostratified: single-layered; all cells touch the basement membrane but may not extend to the top of the membrane • Layers of Cells • Simple: single layer • Stratified: cells are layered on top of one another • Transitional: cell shape & layers differ

16. Glandular Epithelium • Specialized for secretory activity • Unicellular glands • Single celled • Ex: goblet cells • Multicellular glands • Function in clusters, solid cords or specialized follicles

17. Endocrine vs Exocrine • All glands are classified as endocrine or exocrine • Exocrine glands • Discharge/secrete into ducts • Ex: salivary glands • Endocrine glands • “ductless glands” • Secrete hormones directly into blood or interstitial fluid • Ex: pituitary and thyroid glands

18. Structural Classification of Exocrine Glands • (Table 5-2, p. 133) • Shape of gland: • Tubular • Alveolar (sac-like) • Complexity of gland: • Simple (one duct) • Compound – > 2 ducts (branched)

20. Functional Classification of Exocrine Glands • Apocrine • Collect secretory products at apex (tip) • Apex of cell pinches off • Cell repairs itself & repeats process • Ex: milk-producing mammary glands • Holocrine • Collect secretory product inside the cell • Rupture to release (self-destructs) • Ex: sebaceous glands (oil glands) • Merocrine • Discharge through plasma membrane • This type applies to most exocrine glands • Ex: salivary glands

21. Figure 5-12, p. 132

22. Connective Tissue • Most widespread tissue in the body • Functions: • Connection • Support • Transport • Protection • Insulation

23. Characteristics of Connective Tissue • Common origin – mesoderm • Matrix • Intercellular material • Few cells, fibers, fluid, ground substance (material between cells) • Fibers: • Collagenous fibers • Reticular fibers • Elastic fibers

24. Fibers • Collagenous fibers • “white fibers” • Made of collagen (fibrous protein) • Tough, strong • Reticular fibers • Delicate • Reticulin – protein • Support small structures (ex: capillaries) • Elastic fibers • Extensible & elastic • Elastin – protein • Found in “stretchy” tissue (ex: cartilage of the external ear)

25. Classification of Connective Tissue • Fibrous • Loose (areolar) • Adipose • Reticular • dense • Bone • Cartilage • Hyaline • Fibrocartilage • elastic • Blood **Reference Table 5-3, pp. 134-135**

26. Fibrous Connective Tissue • Loose connective (areolar) tissue (fig 5-13) • Stretchable • most abundant connective tissue in the body • Connects adjacent structures • Ex: btwn other tissues and organs • Ex: superficial fascia

27. Fibrous Connective Tissue 2. Adipose tissue (fig 5-14) • Contains mainly fat cells • Supportive/protection pads around kidneys & other body structures • Storage deposit for excess food • Insulating material, conserves body heat

28. Fibrous Connective Tissue 3. Reticular Tissue (Fig 5-16) • 3D web of reticular fibers • Forms the framework of the spleen, lymph nodes & bone marrow • Meshwork filters harmful substances out of the blood

29. Fibrous Connective Tissue 4. Dense Fibrous Tissue (fig 5-17, 5-18, 5-19) • Densely packed fibers • Regular Dense CT • Fibers arranged in regular, parallel rows • Collagen fibers • Flexible, strong • Tendons (muscle to bone) & ligaments (bone to bone) • Irregular Dense CT • Fibers intertwine • Withstand stress from any direction • Ex: dermis (inner layer of skin); outer capsule of kidney & spleen

31. Bone Tissue • We will cover this when we cover the skeletal system • Just know that bone is a type of connective tissue 

32. Cartilage • Only 1 cell type – chondrocyte • Located in lacuna • Avascular – receive nutrients via diffusion • Injuries to cartilage heal slowly due to poor nutrient delivery

33. Cartilage - Types • Hyaline cartilage • Most common • Covers ends of long bones (where joints articulate) • Found in supporting rings of respiratory tubes • Fibrocartilage • Strongest, most durable • Intervertebral disks • Menisci in knee joint • Elastic cartilage • Fine elastic fibers • High degree of flexibility • External ear

35. Blood • Unusual type of connective tissue • No ground substance • Matrix = plasma (55%) • Formed elements = blood cells (45%) • Erythrocytes – RBCs • Leukocytes – WBCs • Thrombocytes – platelets • Transport function • Respiratory gases, nutrients, waste products

36. Anthony’s Textbook of Anatomy and Physiology 17th Edition. Thibodeau, Gary A. PhD and Patton, Kevin T. PhD. Mosby, Inc.