Chapter 4: Tissues
Human tissues are collections of cells and cell products that
Four types of tissues: Epithelial, Connective, Muscular, Nervous
I. Epithelial
• "covering" and “lining”
• form glands
Characteristics of Epithelial Tissue:
• cellularity: formed of closely joined cells – in sheets
• polarity – 2 different surfaces
Apical (exposed)
Basal (attached) surface of cells
• attachment – attached to connective tissue via basal lamina (basement membrane).
• avascular –
• regeneration-
Functions of Epithelial Tissue:
1.) Provide physical protection
2.) Control Permeability (absorption/secretion)
3.) Sensation
4.) Produce secretions
Glandular epithelium
Specializations of Epithelial Cells
Microvilli: extensions of cell membrane on the apical surface
Cilia: hair like structures which beat
Maintaining the Integrity of Epithelia
1.) intercellular connections
2.) attachment to basal lamina
3.) epithelial maintenance & repair
1. Intercellular Connections: anchor cell membranes
cell adhesion molecules (CAMs)
intercellular cement: glycosaminoglycans – hyaluronan
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Cell Junctions – specialized areas in cell membrane
a. Tight (occluding) junctions: impermeable
Lining of intestinal tract – lumen
b. Gap junctions: cells held together by connexons (channel proteins)
c. Desmosomes (macula adherens): in areas subject to mechanical stress
Held with CAMs and proteoglycans
2. Attachment to basal lamina
Two layers:
1.) lamina lucida
2.) lamina densa
3. Epithelial Maintenance and Repair
• cells often only live for days and die/shed
• stem cells (germinative cells) deep and have rapid mitotic rate
• damaged cells quickly replaced
Classified by the number of layers and the shape of cells (Table 4-1 pg. 113)
A. Layers:
simple:
stratified:
B. Shape of Cells:
squamous:
cuboidal:
columnar:
1. Simple Squamous: one layer
-good for
-found in the linings of
-also known as mesothelium and endothelium
2. Stratified Squamous:
-most widespread
-functions:
-found in areas subject to friction: mouth, vagina, anus
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3. Simple Cuboidal: one layer
-have large spherical central nucleus
-found in glands: thyroid & nephron
4. Transitional:
- stretches & recoils without damage
- appearance changes as it stretches
-found in urinary bladder
5. Simple Columnar:
- function for absorption, secretion, protection
-found in lining of
6. Psuedostratified Ciliated Columnar:
-looks striated but it isn’t
- cilia function for?
-found in
Glandular Epithelium
Exocrine vs. Endocrine Glands
Endocrine glands: secrete directly into blood
Secretions termed:
Examples:
Exocrine glands: secrete through ducts
Examples:
modes of secretion (Figure 4-6 pg. 119)
1.) Merocrine: exocytosis of secretions
Salivary glands secrete (mucin) or mucus
Merocrine sweat glands
2.) Apocrine: apical portion of cell shed with secretions
Mammary glands
3.) Holocrine: entire cell ruptures to release secretions
Sebaceous glands
Types of secretions:
1.) serous glands
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2.) mucous glands
glands can be simple or compound in structure
II. Connective
Functions:
1. binds
2. framework for
3. protects
4. storage sites for
&
together & supports structure
cells
5. forms rigid skeletal framework of body
6. limits ROM
7. transports
fights
(defense of body)
Connective tissue consists of few cells with a lot of intercellular matrix (ground
substance)
Classification of Connective Tissues
1.) Connective tissue proper
2.) Fluid connective tissues
3.) Supporting connective tissues
1.) Connective Tissue Proper
• contains fibers, ground substance & cells
Cells associated with connective tissue proper
1. fibroblast:
Secreted hyaluronan and protein fibers
Important for tissue growth & repair
2. macrophages: phagocytes:
3. adipocytes: store fat
4. mesenchymal cells: stem cells
5. melanocytes: produce melanin
6. mast cells: release histamine & heparin
7. lymphocytes: WBC
8. microphages: neutrophils and eosinophils
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Connective Tissue Fibers
A. Collagenous: most abundant – “white fibers”
Inelastic
Strong
B. Reticular: short, thin
C. Elastic:
Types of Connective Tissue Proper:
1. Loose Connective Tissues – “packing peanuts”
Areolar, Adipose, Reticular
A. Areolar: most abundant
•consists mostly of collagenous fibers
•large spaces between cells:
•unorganized fiber arrangement
•functions:
1.attach skin
2. fill spaces
3. surround & support
B. Adipose Tissue:
•functions:
• cells do not undergo mitosis throughout life
• white vs. brown fat
Brown fat very metabolically active
• visceral vs. subcutaneous fat:
Subcutaneous fat found below skin
Visceral found in abdomen (belly fat)
Waist: hip ratio
< 1 ideal (better: <.95 men,
< .8 women)
C. Reticular Connective Tissue:
•similar to loose connective tissue, contains ground substance in network of
interlacing fibers
•make up the inner framework in
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2. Dense Connective Tissues – Connective tissues proper, tightly packed with
high numbers of collagen or elastic fibers
A. Dense Regular Connective Tissue:
• tightly packed bundles of collagenous fibers
• many fibroblasts
1. tendons
2. ligaments
3. fascia
4. aponeuroses
B. Dense Irregular Connective Tissue:
•fibers oriented randomly:
•found in:
1. dermis
2. fibrous coverings: (perichondrium), (periosteum), &
(perineurium)
3. capsules of many organs
C. Elastic Connective Tissue:
•contains more elastic than collagenous fibers
•good for
•found in walls of
2. Fluid Connective Tissues –
A. Blood: watery mix of dissolved proteins
contains formed elements (cells) and plasma
Formed elements: RBC, WBC, platelets
B. Lymph: fluid contains protein, lymphocytes, fats
Similar to interstitial fluid
Circulates via lymphatics
3.) Supporting Connective Tissues: Support soft tissues & body weight
Cartilage
• Gel-type ground substance
• For shock absorption and protection
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Bone
• Calcified (made rigid by calcium salts, minerals)
• For weight support
A. Cartilage
•numerous collagen fibers in a firm matrix contains:
1.) Proteoglycans derived from chondroitin sulfates
2.) Ground substance proteins
3.) Chondrocytes (cartilage cells) surrounded by lacunae (chambers)
•fibers/matrix formed by cells:
-chondroblast:
-chondrocytes
•avascular: due to secretion of antiangiogenesis factor
- surrounded by perichondrium
Outer fibrous layer
Inner cellular layer
Cartilage growth (both stop in adults)
1.) interstitial growth: chondrocyte undergoes mitosis
growth from within cartilage
mainly during embryonic development - adolescence
2.) appositional growth: new layers of cartilage added to surface
-does not occur in adults
Types of cartilage
1. Hyaline:
-most abundant
-provides support & reduces friction
-precursor to bone (fetal skeleton), costal cartilage
-also found in
2. Fibrocartilage (fibrous)
-collagen fibers in thick bundles
-slightly compressible
-found in regions that
-intervertebral discs, knee joint: menisci
and pubic symphysis
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3. Elastic -contains collagen but
-found in
8. Bone or osseous tissue:
• strong mineralized matrix
Calcium & phosphate salts
Resist shattering
•osteoblast:
• osteocyte:
Inside lacunae
Lacunae interconnected with canaliculi
• 2 differences between bone and cartilage:
1. bone well supplied by
2. canaliculi
• surrounded by periosteum
Membranes: physical barriers that line
Consist of: an epithelium supported by
1.) mucous membranes: secrete mucus (sticky)
Found in
2.) serous membranes: line ventral body cavities
Visceral
Parietal
3.) cutaneous membrane: skin
4.) synovial membranes
Fasciae: provides strength, stability, route for blood & lymph vessels
1.) superficial (hypodermis): areolar & adipose tissue
2). deep: dense irregular connective
3.) subserous fascia: areolar tissue
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III. Muscular (Figure 4-18 page 136)
•specialized for
• contains actin & myosin: proteins which produce all body movements
•3 types of muscle tissue: all made up of myosin, actin, collagen
All contract
1. skeletal: largest cells & striated
Found
Appearance: long
multinucleated
Specializations: myosatellite cells (satellite cells) – stem cells for skeletal
muscle
2. cardiac: striated
Cardiocyte – cardiac muscle cell
Found
Appearance:
Specializations: intercalated discs
3. smooth (visceral): nonstriated
Found
Appearance:
IV. Nervous (neural) Tissue (Figure 4-19 pg. 137)
– Specialized for conducting electrical impulses
–
Rapidly senses internal or external environment
–
Processes information and controls responses
–
Forms the brain, spinal cord, nerves
•Two types of cells: neurons & supporting cells (neuroglia)
Neurons: conduct nerve impulses
- 3 parts: dendrite, cell body & axon
Cell body contains organelles
-amitotic
-need continuous supply of?
Neuroglia cells:
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Tissue Response to Injury: (pg. 139)
Tissues respond to injuries to maintain homeostasis
Cells restore homeostasis via:
1.
2.
1. Inflammatory Response (inflammation)
immediately after injury area is isolated while damaged cells and microorganisms are
cleaned up
• infection: presence of pathogens
•Inflammation: short term (acute) inflammation has 4 symptoms:
1.
2.
3.
4.
•what causes this?
1. initial injury causes release of chemicals (histamine, heparin, prostaglandins, bradykini)
from neutrophils, macrophages, mast cells
-these chemicals cause vasodilation of blood vessels which increases blood flow
to injured area = heat, redness
-histamine increases permeability – makes blood vessels “leaky” = swelling
-swelling puts pressure on nerve endings = pain
-why is this good?
1. helps dilute toxins & remove wastes
2. brings oxygen & nutrients
3. brings phagocytes
4. increases temperature
5. brings antibodies
-necrosis: tissue/cell death
lysosomes: release enzymes to destroy injured cells and surrounding area –
produces debris, fluid, dead/dying cells known as pus
abcess: accumulation of pus in enclosed tissue space
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2. stasis: "standing"
-slowdown of blood flow
Repair: 2 major ways:
1. regeneration:
2. fibrosis: scar tissue
Read the text pages 138, 140 on aging, tissue structure & cancer. Also read Applications Manual
page 40 - Tissue Structure and Disease.
Inflammatory Conditions:
Arthritis
Asthma
Colitis:
TX:
Ice therapy:
Non-steroidal anti-inflammatory drugs (NSAIDs – such as aspirin, ibuprofen or naproxen)
Corticosteroids (such as prednisone)
Note:
C-reactive protein (hs-CRP) assay: measures levels of C-reactive protein
Increases during acute inflammation
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