Lecture 2- Connective Tissue

Question 1

Connective Tissue

Answer 1

-Most abundant tissue
-Provides supportive and connecting framework (stroma) connect, anchor, support
-Role in storage of metabolites, immune/inflammatory responses, tissue repair
Composition: -Cells and Exctracellular matrix (ECM) made of fibers and proteoglycans (ground substance)
-Cells widely scattered in matrix
-Matrix secreted by cells (is not living)
-Highly vascularized

Question 2

Fibroblasts

Answer 2

• Star shaped w oval nucleus
• Most numerous
• Produce ECM by synthesizing/secreting mature proteoglycans, glycoproteins, precursor molecules of collagens/elastins
• Wound repair

Question 3

Macrophages

Answer 3

• Phagocytic, derived from monocytes
• monocytes migrate from blood to tissue, then mature into macrophages (Kupffer cells-liver, Osteoclasts-bones, Microglial cells-CNS)
• very granular
• mobile
• have many lysosomes

Question 4

Plasma Cells

Answer 4

• From differentiation of B lymphocytes
• Synthesize/secrete immunoglobulin (antibodies)
• Prominent cartwheel nucleus w well developed nucleolus
• Abundant rough ER and golgi
• Move throughout ECM

Question 5

Mast Cells

Answer 5

• Mast cells/basophils have same progenitor in bone marrow
• Found around blood vessels
• Produce heparin (anticoagulant)
• Produce histamine (vasodilator)

Question 6

Fat Cells (adipocytes)

Answer 6

• Storage of energy

- Protection

Question 7

Pigment Cells (Melanocytes)

Answer 7

• Produce melanin

- Protection from UV

Question 8

Extracellular Matrix

Answer 8

-Binds supports and surrounds cells and fibers
Fibers: -Collagen -Elastin -Reticular Fibers
Ground Substance

Question 9

Collagen Fiber

Answer 9

• Protein collagen arranged in bundles
• Most abundant of fibers
• parallel rubbing fibrils for strength
• white/yellow
• soft/flexible/strong
• not elastic or extendable
• Vit C is cofactor for synthesis
• lack of collagen = scurvy = inadequate wound healing

Question 10

Elastic Fiber

Answer 10

• protein elastin
• thin, yellow
• stretch and return to normal
• connect to one another

Question 11

Reticular Fibers

Answer 11

• protein collagen and glycoproteins
• similar to collagen, thinnest/most delicate
• form reticular framework

Question 12

Ground Substance

Answer 12

• Viscous material, holds cells together
• hyaluronic acid
• Mucopolysacharide
• Mucoproteins

Question 13

Connective Tissue Classification

Answer 13

Embryonic CT
Adult CT: -Loose
-Dense: regular/irregular -Reticular -Elastic
Special CT: -Adipose: white/brown -Cartilage: hyaline/elastic/fibrocartilage -Bone: compact/woven/cancellous

Question 14

Embryonic CT

Answer 14

• present in ebryo/umbilical cord
  1. mesenchyme: found primarily in embryo, made of spindle shaped cells in contact w neigboring cells, mand reticular fibers w few collagen fibers
  2. Mucous CT: in umbilical cord. Made of homogenous ground substance, jelly like, calld Whartons jelly

Question 15

Adult CT: Loose & Dense Irregular CT

Answer 15

1. Loose (areolar) irregular CT: -loosely arranged fibers and abundant cells
   - beneath epithelia and lines internal surfaces of body
   - site of inflammatory/immune responses
2. Dense irregular CT: -abundant fibers and few cells
   - mainly collagen arranged in bundles oriented in various directions that can stand stress on organs
   - In sub mucosa of intestinal tract, deeper layer of dermis

Question 16

Adult CT: Dense Regular

Answer 16

• Ordered and densely packed arrays of fibers and cells and very little ECM
• fibers are arranged in parallel arrays and provide maximum strength
• Main functional component of tendons, ligaments, and aponeuroses

Question 17

Adult CT: Reticular Tissue

Answer 17

-Reticular fibers provide a supporting framework for cellular constituents of various tissues and organs

Question 18

Adult CT: Elastic Tissue

Answer 18

• Mainly composed of elastic fibers and capable of stretch and distension
• Fibers are Thinner than collagen, aranged in branching patterns
• Found in dermis, aorta, vertebral ligaments, larynx

Question 19

Special CT: Adipose Tissue

Answer 19

-Important role in energy homeostasis
White: -predominant type in adults -serves to store energy, insulation, cushioning of vital organs, secretion of hormones -Unilocular cells w single large fat inclusion that pushes nucleus to side
Brown: -abundant in newborns ~5% of body weight, found in back by upper half of spine toward shoulders, very reduced in adults -multilocular, rich in mitochondria, surrounded by lots of blood vessels

Question 20

Special CT: Hyaline Cartilage

Answer 20

• avascular
• surrounded by perichondrium (except in articular cartilage)
• made of chondrocytes surrounded by collagen matrix
• occurs in temporary skeleton of embryo, articular cartilage, cartilage of nose larynx trachea bronchi costal cartilages

Question 21

Special CT: Elastic Cartilage

Answer 21

• avascular
• surrounded by perichondrium (except in articular cartilage)
• made of chondrocytes surrounded by matrix of elastic fibers and collagen fibers
• In external ear epiglottis and auditory tube

Question 22

Special CT: Fibrocartilage

Answer 22

• Genrally avascular
• lacks perichondrium
• made of chondrocytes, fibroblasts, surrounded by collagen fibers and less rigid ECM
• Found in intervertebral discs, articular discs of knee, strenoclavicular joints, pubic symphysis

Question 23

Special CT: Bone

Answer 23

Structure: 1.Compact/dense bone 2.Spongy/cancellous/trabecular bone based on collagen fiber organization 1. Lamellar bone (consists of lamellae made of bone matrix and osteocytes in lacuna w radiating canaliculi 2.woven/nonlamellar bone
Lamellae types:
1. Osteons/haversian system: concentric arranged lamellae around a longitudinal vascular channel
2. Interstitial lamellae: between osteons
3. Outer circumfrential lamellae: just under periosteum
4. Inner circumfrential lamellae: close to endostem
Vascular Channel Orientation:
1. Longitudinal capillaries and post capillary venules run in center of osteon called haversian canal
2. Transverse/oblique/Volkmann’s canals contain blood vessels from marrow/periosteum and connect haversian canals
Bone matrix: organic and inorganic components
Bone Cells: osteoblast and osteoclast lineage

Question 24

Bone Repair After Fracture

Answer 24

• Neutrophils arrive to injury first, followed by macrophages that clear up injury site
• Fibroblasts and capillaires proliferate and grow into injury site
• Loos granulation tissue (scar) is formed and cartilage forms in parts of it, fibroblasts and periosteal cells contribute to this step
• Dense connective tissue and newly formed cartilage grow, covering bone at fracture site and producing soft callus. Callus helps stabilize/bind together fracture bone
• 6-12 week process

Question 25

Dupuytren’s Disease

Answer 25

-Continued remodeling results in hypertrophic scar w excessive connective tissue contracture