Histology Lab Terms

Question 1

Epidermis

Answer 1

the most superficial layer of skin comprised of stratified squamous orthokeratinized epithelium. Separated from the underlying dermis y a very thin basement membrane

Question 2

Stratified Squamous orthokeratinized epithelium

Answer 2

multilayered tissue wherein the most superficial livings cells are flattened and then covered by a noncellular layer of keratin

Question 3

Keratinocyte

Answer 3

most common cell type in the epidermis. Creates morphological epidermal strata as it moves upward through the epithelium. After cell death the keratin cytoskeletal elements remain as a protective covering layer on the surface of the integument

Question 4

Stratum Basale

Answer 4

single layer of epidermal cells located immediately above the basement membrane. Anchors the epithelium and is the location of keratinocyte mitotic activity

Question 5

Stratum Spinosus

Answer 5

variability multilayered stratum immediately above the stratum basal. Due to the shrinkage artifact, strong desmosome cell junctions are visible at high mag as very fine linear projections perpendicular to the keratinocyte surface

Question 6

Desmosome

Answer 6

Node of bizzozero
very strong, spot-weld type junction incorporating both intracellular proteins and extracellular proteins to provide exceptional mechanical adhesion b.w keratinocytes. Due to shrinkage artifact, appear as thin linear projections extending perpindicullarily from the surface of the keratinocytes in the stratum spinosus

Question 7

Stratum Granulosum

Answer 7

the most superficial layer of keratinocytes still living at the time of tissue preparation. These squamous shaped cells are only a few layers think and have a granular appearance due to the presence of keratohyaline

Question 8

Stratum Lucidum

Answer 8

usually a thin light stained layer of noncellular sheets of keratin/keratinohyalin located immediately above the stratum granulosum, absent in hairy skin

Question 9

Stratum Corneum

Answer 9

the bulk of non-cellular sheets of keratin/keratinohyaline located most superficially in the epidermis. This layer is thin in hairy skin and think in glabrous skin

Question 10

Keratin

Answer 10

the intermediate filament cytoskeleton protein present in epithelial tissues. Incorporated into desmosomes and visible as sheets in stratum lucid and stratum corneum

Question 11

Clear Cell of the epidermis

Answer 11

Melanocytes, Langerhans Cell, Merkel Cells
synthesizes and secretes pigment which is then picked up and stored by keratinocytes. Appears as a clear staining cell in the stratum basale

Question 12

Rete Peg

Answer 12

extension of the epidermal stratifies squamous orthokeratinized epithelium down towards the underlying dermis. Contributes to the overall adhesion between the dermis and epidermis

Question 13

Basement Membrane

Answer 13

very thin, non cellular sheet of glycoproteins located at the epithelial tissue interface. Serves as an anchor and filter for the epithelial compartment. Although not directly visible, its location can be identified by the dramatic morphological change present at the epidermal/dermal layer

Question 14

Dermis

Answer 14

intermediate layer of skin comprised primarily of dense irregular connective tissue. This layer provides physical and physiological support to the overlying epidermis and is also location for the glands and many of neuromuscular elements of integument

Question 15

Dense Irregular Connective Tissue

Answer 15

comprised of thick or coarse Type I collagen fibbers bundle in a disorganized or irregular pattern. Many cell types will likely be present with the most common being fibroblasts or fibrocytes

Question 16

Fibroblast/Fibroblast

Answer 16

cell responsible for synthesis of the noncellular components of various general connective tissues. Although the cytoplasm of this cel is often not directly visible, the nucleus is visible as small, flattened, heterochromatic and either oval or round. This most common cell type in the dermis

Question 17

Dermal Papilla

Answer 17

projection of the dermal dense irregular connective tissue up toward the overlying epidermis. Contributes to the overall adhesion between the dermis and epidermis.

Question 18

Papillary Dermis

Answer 18

relatively thin, uppermost region of the dermis inclusive of the dermal papillae and the intervening segments of dermis deep to the rate pegs. Comprised of dense CT usually with no clear demarcation between papillary and reticular dermis

Question 19

Hypodermis

Answer 19

deepest layer of the integument comprised primarily of adipose. Equivalent to superficial fascia in gross anatomy

Question 20

Adipose

Answer 20

special type of CT comprised almost entirely of large cells bound to each other by very thing strands of Type I collagen and packaged into bundles of cells by thin seems of dense irregular CT

Question 21

Seat Glands

Answer 21

tubular expansion of the epithelium away from the epidermis usually to a point pairly deep to the reticular dermis. The secretory portion of this tubular gland is coiled upon itself deep within the dense irregular CT of reticular dermis and the loops this coiled gland are entwined by loose CT. The excretory duct of this tubular gland spirals up through the dermis and epidermis and opens via a pore at the surface. As this gland is unbranched along its entirety it is known as a simple tubular gland

Question 22

Loose Connective Tissue

Answer 22

comprised of very thin, delicate collagen fibbers in a disorganized or irregular pattern. When associated with sweat glands the only cell type likely to be seen is fibroblast/fibrocyte

Question 23

Hair Follicle

Answer 23

large invagination of the epidermal epithelial cells deep into the reticular dermis. The base of the follicle, knows as the bulb, is the ovation for synthesis of the noncellular hair shaft. The root sheath refers to the cells surrounding the hair shaft and extending from the bulb to the epidermis

Question 24

Arrector Pili muscle

Answer 24

a relatively narrow slip of smooth muscle originating from the side of the root sheath and angling some distance into the surrounding dermis. When contracted, this muscle causes the follicle to become slightly more erect and produces a slight bulce in the integument surface

Question 25

Sebaceous Gland

Answer 25

globular cluster of densely packed, pale staining cells extending from the side of the hair follicle. Each cluster of cells typically has its own duct leading into the follicle hence the gland is known as a simple acinar gland

Question 26

Meissner’s Corpuscle

Answer 26

relatively small sensory receptor for light touch. Located within the dermal papilla and has appearance akin to a cocoon or giant mitochondria

Question 27

Pacinian Corpuscle

Answer 27

relatively large sensory receptor for deep pressure. Located near the dermal/hypodermal interface and has appearance akin to a topographical map or a sagitally sectioned onion

Question 28

Dense Regular CT

Answer 28

comprised of thick or coarse Type I collagen fibbers bundles in a highly organized and parallel pattern. The only likely cell type present here are fibroblast/fibrocyte.

Question 29

Collagen

Answer 29

most common fibrous extracellular matrix protein found in most CT. Variable in thickness, often wavy and usually stains pink

Question 30

Hyaline Cartilage

Answer 30

slide specimen taken from trachea. The matrix appears smooth because the Type II collagen present is too thin to be resolved with light microscopy. The matrix is produced and maintained by chondroblasts/chondrocytes. No other cell types or structures are located in cartilage. This tissue is surrounded by a transitional perichondrium which blends characteristics of the cartilage with the adjacent general CT

Question 31

Lacuna

Answer 31

the space in the extracellular matrix where a chondrocyte was located. Most visible as a hole in the cartilage matrix when the cell is absent

Question 32

Chondrocyte

Answer 32

relatively large, round cell located withith the matrix lacuna of any of the three types of cartilage. Responsible for maintaining cartilage matrix and, as such, is relatively inactive

Question 33

Isogenous Group

Answer 33

a cluster of chondrocytes and their associated lacunae. Indicitive of rapid mitotic cell division and/or slowing of interstitial growth. Each of the cells within the group are descendants of a single parental chondrocyte

Question 34

Chondroblast

Answer 34

relatively small, ovoid cell located in the chondrogenic perichondrium of hyaline and elastic cartilage. Primarily responsible for new cartilage matrix deposition and, as such, is relatively active

Question 35

Chondrogenic Perichondrium

Answer 35

the inner portion of the perichondrium containing chondroblasts and a matrix very similar to the cartilage. Site for appositional growth.

Question 36

Fibrous Perichondrium

Answer 36

the outer portion of the perichondrium containing fibroblasts and a matrix very similar to those surrounding tissues

Question 37

Perichondrium

Answer 37

general term for the transitional tissue surrounding hyaline and elastic cartilage. Inclusive of both the chondrogenic and fibrous layers. Contains the cartilage vascular supply and is the source for much of the cartilage growth and repair

Question 38

Epiphysis

Answer 38

either end of a long bone. Can be made of hyaline cartilage. The hyaline cartilage is being replaced by bone via a mechanism known as endochondral ossification

Question 39

Diaphysis

Answer 39

the shaft of long bone. The marrow cavity is surrounded by a relatively think shell of compact bone. Traversing through the marrow cavity are small bony spicules collectively known as spongy bone

Question 40

Marrow Cavity

Answer 40

central region of bone housing the hemtopoietuc cells and spongy bone.

Question 41

Compact and Cortical Bone

Answer 41

relatively thick shell of bone forming the periphery of the diaphysis. Contains osteocyts in lacunae and is lined internally by endosteum and externally by periosteum,

Question 42

Spongy or Cancellous Bone

Answer 42

collection of relatively thin bony spicules traversing thru the marrow cavity. At a later time, when endochondral ossification advances to completion, this bony pattern will occupy the entire epiphysis. Usually appears as bony islands scattered thru the diaphysis

Question 43

Endosteum

Answer 43

layers of cells lining the inner surface of the compact bone and eventually the spongy bone surfaces as well. This layer of cells provides for growth and remodelling of the compact bone inwardly towards the marrow cavity

Question 44

Periosteum

Answer 44

transitional layer of tissue covering the outer surface of the compact bone. Note its absence on the articular surface of the epiphysis

Question 45

Osteogenic Periosteum

Answer 45

the inner portion go the periosteum primarily containing osteoblasts. This layer of cells provides for growth and remodelling of the compact bone outwardly

Question 46

Fibrous Periosteum

Answer 46

the outer portion of the periosteum primarily containing fibroblasts and general CT matrix. Typically blends with tissue surrounding the bone

Question 47

Osteocye

Answer 47

responsible for the maintenance of existing bone matrix. Limited in location to lacunae within compact or spongy bone

Question 48

Osteoclast

Answer 48

responsible for the resorption of existing bone matrix. Comparitively large, multinucleate cell located on the resorbable surface including endosteum and osteogenic periosteum

Question 49

Osteoblast

Answer 49

responsible for the deposition of new bone bone matrix. Has a smack, flattened oval, heterochromatic nucleus and is located on a growable surface including endosteum and osteogenic periosteum. Also present on developing bony spicules in the zone of ossification.