HUMAN ANATOMY

1. HUMAN ANATOMY LECTURE FOUR TISSUES (Part 2)

2. CONNECTIVE TISSUE • Characterized by cells separated by an extracellular matrix (protein fibers and ground substance) • Variety of Functions: - encloses organs as a capsule and separates tissues/organs into layers - connects tissues together (tendons and ligaments) -support and movement (bones) - storage (fat) - cushioning and insulation (fat) - transportation (blood) - protection (blood, immune system, bones)

3. CONNECTIVE TISSUE CELLS Fibroblasts – always present, most common - secrete hyaluronan (like cement) and proteins for the matrix Adipose or Fat Cells (adipocytes)– common in some tissues (skin) and rare in others (cartilage) Mast Cells – common beneath membranes, along small blood vessels - release heparin, histamine, and proteolytic enzymes (cause inflammation in response to injury) White Blood Cells – move between blood vessels and connective tissue - respond to injury or infection

4. Macrophages – provide protection by phagocytosis of pathogens or damaged cells (i) Fixed – stay in connective tissue (ii) Wandering – move through connective tissue Undifferentiated Mesenchyme (stem cells) – have potential to differentiate into various adult cells Melanocytes – synthesize and store melanin - common in the eye and dermis of skin

5. EXTRACELLULAR MATRIX PROTEIN FIBERS Composed of three types: • Collagen - like strong ropes, flexible, inelastic (STRENGTH) • Reticular - fine, short collagen fibers (SUPPORT) - strong but flexible because of branching - fill spaces between tissues and organs • Elastic – contain elastin (protein), branched and wavy structure - ability to recoil after being stretched (ELASTIC)

6. EXTRACELLULAR MATRIX GROUND SUBSTANCE Dense material containing cells and protein fibers: • Hyaluronic acid - polysaccharide - good lubricant • Proteoglycans- protein and polysaccharide - protein attaches to hyaluronic acid and traps large amounts of water • Adhesive Molecules – holds proteoglycan aggregates together

7. CONNECTIVE TISSUE TERMINOLOGY Related word stems: -blasts: create the matrix ie: osteoblast -cytes: maintain the matrix ie: fibrocyte -clasts: break the matrix down ie: chondroclast Fibro… = fibrous connective tissue cells Chondro… = cartilage cells Osteo… = bone cells

8. TYPES OF CONNECTIVE TISSUE Based on physical properties: (1) Loose (areolar) - loosely arranged collagenous fibers (2) Dense - fibers in thick bundles that nearly fill all the extracellular space - dense regular, dense irregular (3) Supporting Connective Tissue – cartilage (hyaline, fibrocartilage, elastic), bone (4) Fluid Connective Tissue - blood

9. LOOSE CONNECTIVE TISSUE • Loosely woven fibers with many cells • Fill spaces between and within organs • Surround nerves and blood vessels

10. Areolar Tissue • Loose packing material between organs and tissues – STROMA • Attaches skin to underlying tissue • Provides padding, separation of skin from underlying movement • Supports blood vessels and nerves • Contains collagen, reticular, elastic fibers and all cells types

11. Adipose Tissue • Contains adipocytes (fat cells) with very few fibers or matrix • Protection, padding, insulation around organs Yellow (white) - most common with wide distribution - small ring of cytoplasm surrounding single large lipid droplet, nucleus flattened and eccentric - white at birth, yellows with age Brown - found in specific areas: axillae, neck, near kidneys - highly vascularized

12. Reticular Tissue • Network of reticular fibers • Creates supportive stroma for organs (liver and spleen)

13. (2) DENSE CONNECTIVE TISSUE • Made up mainly of fibers (mostly collagen) • Few cells (fibroblasts) with little matrix

14. Dense Regular • Mainly collagen fibers • Fibers all aligned in same direction (parallel) • Very strong, able to withstand great pulling forces in direction of fiber orientation - tendons (muscle to bone) - ligaments (bone to bone) - aponeurosis (muscle to muscle or several bones)

15. Dense Irregular • Fibers arranged randomly • Add strength to areas that are stressed in different directions ie: innermost layers of dermis, scars, capsules of organs, joint cavities

16. Dense Regular Elastic • Regular, orderly arrangement of fibers • Collagen fibers for strength • Elastin fibers for stretching and recoiling • Found in vocal cords - nuchal ligament

17. Dense Irregular Elastic • Bundles and sheets of collagenous and elastic fibers oriented in multiple directions • Strong yet elastic • Found in walls of arteries

18. (3) SUPPORTING CONNECTIVE TISSUE • Provide strong framework for supporting the body • Includes: cartilage and bone

19. Cartilage • Composed of chondrocytes (cells) in a firm gel matrix (protein fiber, ground substance and fluid) - fibers are collagen and sometimes elastin - ground substance of proteoglycans and hyaluronic acid complexed together to trap water • Spaces around chondocytes are called lacunae • Avascular with no nerve supply – heals slowly • Perichondrium – dense irregular connective tissue surrounding cartilage. - has fibrous layer and inner cellular layer - fibroblasts can differentiate into chondroblasts (healing and growth) • 3 types of cartilage:

20. (i) Hyaline Cartilage • Most common type • Closely packed collagen fibers in proteoglycan matrix - tough but flexible • Smooth, covers ends of bones and joints (can withstand repeated compression), sternum, ribcage, nasal passage, respiratory tract, embryo skeleton • Involved in growth that increases bone length

21. (ii) Fibrocartilage • Bundles of interwoven collagen fibers (more fibers than ground substance) • Slightly compressible and very tough, withstands pulling and tearing • Found where great pressure applied to joints: knee, jaw, between vertebrae of spine, around tendons • Areas like the knee contain both types of cartilage - hyaline covers bony surface, fibrocartilage prevent contact between bones

22. (iii) Elastic Cartilage • Contains mainly elastic fibers, some collagen • Rigid but flexible - recoils back when stretched • Forms flap (pinnae) of external ear, epiglottis, auditory tube

23. Bone • Hard connective tissue composed of living cells (osteocytes) in lacunae (spaces) within a mineralized matrix • Very small amount of ground substance • Matrix composed of 2/3 calcium salts (calcium, phosphate) and 1/3 collagen fibers - gives strength and rigidity: allows bone to support and protect other tissues and organs • Surrounded by periosteum – connects to tendons and ligaments • Two types of bone: • Cancellous or spongy bone • Compact bone

24. Cancellous Bone • Spaces inbetween – like a sponge • Ends of bones and inside bones Compact Bone • Bone arranged in concentric circular layers around a central canal containing a blood vessel • Found on outside of bones

25. (4) FLUID CONNECTIVE TISSUEBlood • Liquid matrix (plasma) lacking fibers • Contains formed elements (RBC’s, WBC’s, platelets) • Flows through vessels

26. Hemopoietic Tissue • Forms blood cells • Found in bone marrow • Types of bone marrow: Red - hemopoietic tissue surrounded by framework of reticular fibers. Produces red and white blood cells. Yellow – yellow adipose tissue • As children grow, yellow replaces much of red marrow

27. MUSCLE TISSUE • Characteristics: - muscle cells contain specialized contractile proteins (actin and myosin) - contracts or shortens with force - moves the body and pumps blood • Types: Skeletal - attaches to skeleton and enables body movement - striated (striped) and voluntary Cardiac - heart muscle - striated and involuntary Smooth - forms walls of organs, around skin and eyes - unstriated and involuntary – controlled by nervous system

29. NERVOUS TISSUE • Form spinal cord, brain, neurons • Responsible for coordinating and controlling bodily activities • Neurons (nerve cells) – have ability to produce electrical signals (action potentials) • Neuroglia – support cells that nourish, protect, insulate neurons

30. MEDICAL CONDITIONS Marfan’s Syndrome • abnormal fibrillin causes connective tissue to loose strength and elasticity • weakened cardiovascular system - possible bursting of major arteries Osteoporosis • reduction in bone strength, related to exercise, calcium, age Aging • tissues thin, become fragile, bones become brittle Malignant Melanoma • malignant skin tumors originate from melanocytes (pigment producing cells) due to genetics, sun exposure • abnormal mole formation • malignant cells migrate to other areas of the body

31. SOMETHING TO THINK ABOUT • In tendons, collagen fibers are orientated parallel to the length of the tendon. In the skin, collagen fibers are orientated in many directions. What are the functional advantages of the fiber arrangements in tendons and in the skin? • A man was suspected of a gruesome murder in which an object was used to repeatedly stabbed and cut the victim. The police found a towel with blood and some tissue on it in the man’s apartment. He claimed he scraped his hand in a fall on the stairs. After examining the towel, a piece of tissue with rigid but clear matrix and lacunae was identified. Explain why the man’s story is very unlikely. • Explain why it is advisable to suture large wounds.