LECTURE - Connective Tissue, Cartilage, Bone, and Skin

Question 1

What is connective tissue?

Answer 1

• basic tissue type of mesodermal origin
• provides structural and metabolic support for other tissues/organs throughout body:
  > loose ‘packing material’ bw cells
• dense structural support
• exchange of nutrients, metabolites, and waste products
• energy storage and thermal regulation
• immune system
• tissue repair

Question 2

responsible for tensile strength

Answer 2

collagen

Question 3

main fiber in CT; most abundant protein in body

Answer 3

collagen

- polymers of tropocollagen

Question 4

type I collagen

Answer 4

fibrous connective tissue

Question 5

type II collagen

Answer 5

hyaline cartilage

Question 6

type III collagen

Answer 6

• reticulin
• supporting meshwork
• silver stain positive

Question 7

type IV collagen

Answer 7

basement membranes

Question 8

type VII collagen

Answer 8

anchoring fibrils

Question 9

protein responsible for stretch/recoil

Answer 9

elastin

• skin, lung, blood vessels
• synthesized by fibroblasts
• tropoelastin
• requires presence of structural glycoprotein = fibrillin

Question 10

gel-like material that allows pasage of molecules through connective tisue

Answer 10

ground substance

- consists of glycosaminoglycans

Question 11

glycosaminoglycans

Answer 11

• long unbranched polysaccharide chain => small mass, large vol
• negatively-charged hydrophilic side groups = extracellular fluid
• ex: Hyaluronic acid

Question 12

interface between CT and parenchymal cells (epithelium)

Answer 12

basement membrane

- lamina lucia, lamina densa, lamina fibroreticularis

Question 13

white fat

Answer 13

• large lipid droplets
• 20-25% of body weight in normal well-nourished adults
• energy store, thermal insulator, shock absorber

Question 14

brown fat

Answer 14

• small lipid droplets
• abundant mitochondria
• non-shivering thermogenesis (mitochondria uncoupling)
• hibernating animals, newborn mammals

Question 15

rigid protective and supporting framework; deposition of calcium salts within collagen and matrix

Answer 15

bone

Question 16

smooth articular surface at ends of bone structural support in special areas (eg, ears), new bone formation

Answer 16

cartilage

Question 17

joints

Answer 17

composite structures joining bones and permitting varying degrees of movement

• ligaments: bone-to-bone connections (stabilize joints); ACL
• tendons: bone-to-muscle connections (move joints); Achilles’ tendon

Question 18

cartilage

Answer 18

semi-rigid nature due to predominant ground substance within ECM

Question 19

different types of cartilage vary in amount and nature of fibers:

Answer 19

• hyaline: few fibers; lots of ECM
• fibrocartilage: abndant collagen fibres
• elastic: elastic fibers

Question 20

development of cartilage

Answer 20

precursor chondroblasts grow and synthesize ground substance/fibers => trapped mature chondrocytes maintain cartilage matrix

Question 21

hyaline cartilage

Answer 21

• nasal septum
• larynx
• tracheal rings
• most articular surface
• sternal ends of ribs
• developing skeleton
• found where we need flexibility*

Question 22

fibrocartilage

Answer 22

• intervertebral discs
• pubic symphysis
• some joints
• alternating layers of hyaline cartilage and dense collagen
• tensile strength

Question 23

elastic cartilage

Answer 23

• external ear/auditory canal
• epiglottis
• parts of larynx
• walls of Eustachian tubes
• similar hyaline but with numerous elastic fibers (stained black due to affinity for silver salts)

Question 24

osteoid

Answer 24

ECM (type I collagen) that become mineralized calcium hydroxyapatite

Question 25

synthesize osteoid, line up on surface of bone

Answer 25

osteoblasts

Question 26

inactive osteoblasts trapped within bone

Answer 26

osteocytes

Question 27

multinucleated phagocytes that erode bone and facilitate resorption/remodeling

Answer 27

osteoclasts

Question 28

trabeculae

Answer 28

network of fine irregular plates within cancellous (medullary bone)

Question 28

components of long bones

Answer 28

- compact (cortical): dense walls of diaphysis (shaft) - cancellous (medullary) bone: central medullary cavity; network of fine irregular plates called trabeculae - periosteum: dense fibrous layer covering external surface - joint surfaces protected by hyaline cartilage

Question 29

diarthrosis

Answer 29

- synovial joint - joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones - constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulating surfaces.

Question 30

non-synovial joints

Answer 30

- limited movement - syndesmoses (dense fibrous tissue): sutures between bones of skull > replaced by bone with age => synostoses - synchondrosis (hyaline): connection between first rib and sternum (little it of movement) - symphyses (fibrocartilage): pubic symphysis, intervertebral discs

Question 31

tough, flexible straps/cords of collagen fibers that connect muscles to bone

Answer 31

tendons

Question 32

largest organ in body (weight, SA)

Answer 32

SKIN | - marked site-specific function

Question 33

functions of the skin

Answer 33

- protection (UV, chemical, thermal, mechanical) - sensation (touch, pressure, pain, temperature) - thermoregulation (heat loss, retention) - metabolic functions (vit D3 synthesis) - physical appearance (skin, hair, nails)

Question 34

three main layers of the skin

Answer 34

- epidermis: stratified squamous epithelium; produces a surface layer of protein = keratin - dermis: fibrocollagenous and elastic tissue, blood vessels, nerves, sensory receptors; skin appendages (mainly here)= hair follicles, sweat glands, sebaceous glands - subcutis/hypodermis: mainly adipose tissue, larger blood vessels that supply dermis

Question 35

epidermis

Answer 35

self-regenerating stratified squamous epithelium | - keratin, melanocytes, Langerhans cells Merkel cells

Question 36

dermis

Answer 36

- horizontally arranged collagen ad elastic fibres, fibroblasts - blood vessels, sensory organs - skin appendages (eg: eccrine gland and ducts)

Question 37

subcutis

Answer 37

adipose tissue | dermal collagen extensions

Question 38

layers of the epidermis

Answer 38

- stratum corneum = lack nuclei - stratum lucidum - stratum granulosum = kerattohyaline granules - stratum spinosum = cytokeratin -> tonofibrils, desmosomes - stratum basale = mitotic figures

Question 39

'prickle cell layer'

Answer 39

- stratum spinosum | - bundles of tonofibrils converge into numerous desmosomes that form contacts between adjacent kerainocytes

Question 40

melanocytes

Answer 40

- derived from migrating neural crest cells - positive with S100 stain - produce melanin for skin/hair pigmentation, UV protection - scattered in basal layer (stratum basale); more numerous in sun-exposed sites - similar in # between light and dark-skinned individuals; differences in synthetic activity (more active cells in darker indivs)

Question 41

hair follicles

Answer 41

- for thermoregulation, display - three phases: > active growth (ANAGEN) > involution (catagen) > resting (telogen)

Question 42

sebaceous glands

Answer 42

- secrete sebum (waterproofing) - majority associated with hair follicles; exceptions = nipple-areola, eyelids, buccal/labial mucosa - surround hair follicle and discharge holocrine lipid secretions or sebum onto hair shaft - arrector pili muscle inserts below sebaceous glands

Question 43

eccrine glands

Answer 43

- secrete sweat (thermoregulation) - widespread (esp. palms, soles, forehead, axilla) - coiled secretory glands: deep dermis/upper subcutis; outer layer of contractile myoepithelial cells - eccrine ducts: double layer of epithelial cells, inner cuboidal; microvilli lining lumen, biochemically active (modify water, NaCl composition of sweat)

Question 44

apocrine glands

Answer 44

- scent production in animals (less in humans) - mainly nipple-areola, axilla, groin - large glands w/ dilated lumen, eosinophilic budding with apical budding, myoepithelial cell layer - secrete into adjacent hair follicle viaduct similar to sweat glands - viscid milky secretion => becomes malodorous after action of skin commensal bacteria (not functional until puberty)

Question 45

epidermal skin appendages (4)

Answer 45

- hair follicles - sebaceous glans - eccrine glands - apocrine glands

Question 46

overall skin thickness depends on these layers

Answer 46

dermis and subcutis > eyelids: both layers thin > buttocks/back: dermis thick, subcutis usually thick - collagen and elastic fibers; progressive degeneration of upper dermal collagen and elastin with age = wrinkling + loss of texture - dermis = skin appendages, most vascular supply + nerves, sensory endings

Question 47

Layers of dermis

Answer 47

``` - papillary dermis: > fine interlacing collagen and elastin > small vessels, lymphatics and fine nerve twigs - reticular dermis: > larger collagen bundles and elastin fibres > larger vessels and nerves > skin appendages > widely variable thickness ```

Question 48

composed of predominantly mature adipose tissue

Answer 48

subcutis - partially compartmentalized by vertical fibrous septa from lower dermis - some sites contain anagen hair follicles (scalp), apocrine glands (axilla, groin), eccrine (palms, soles), skeletal muscle (face)

Question 49

what skin layer derives its name from abundant desmosomes present?

Answer 49

stratum spinosum

Question 50

surround hair follicle and discharge holocrine lipid secretions onto hair shaft

Answer 50

sebaceous glands | - arrector pili muscle inserts below sebaceous gland