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Histology & Embryology > Midterm > Flashcards

Midterm Flashcards

0
Q

Types of Simple Epithelium

A

Single layer, very delicate.

  1. Simple squamous
  2. Simple cuboidal
  3. Simple columnar
  4. Pseudostratified columnar
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1
Q

Types of Epithelium

A
  1. Covering/lining tissues

2. Glandular

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2
Q

Simple Squamous Epithelium

A

Cells are flat, line walls of blood and lymph vessels

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3
Q

Simple Cuboidal Epithelium

A

Cells are cube shaped, covers ovaries & duct systems of salivary glands

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4
Q

Simple Columnar Epithelium

A

Cells are tall & narrow, lines cervix of the uterus

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5
Q

Pseudostratified Columnar Epithelium

A

A type of simple epithelium. Appears stratified, lines upper respiratory tract.

  • Cilia: filter
  • Goblet cells: secrete
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6
Q

Types of Stratified Epithelium

A

Several layers thick.

  1. Stratified squamous
  2. Stratified cuboidal
  3. Stratified columnar
  4. Stratified transitional
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7
Q

Stratified Squamous Epithelium

A

Overall, cells are flat.

  • keratinocytes
  • several layers
  • major component is keratin
  • contains no blood vessels
  • keratinized: epidermis
  • *parakeratinized: masticatory mucosa (gingiva, hard palate)
  • nonkeratinized: lining mucosa (JE, labial & buccal mucosa, ventral surface of tongue, floor of mouth, col region)
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8
Q

Stratified Cuboidal Epithelium

A

Cube shaped.

  • several layers
  • lines ducts of sweat and sebaceous glands
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9
Q

Stratified Columnar Epithelium

A

Tall & narrow.

  • several layers
  • line pharynx & larynx
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10
Q

Stratified Transitional Epithelium

A

Modified cuboidal

  • lines urinary tract and bladder
  • can change shape, cube to flat
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11
Q

Layers of Stratified Squamous Epithelium

A
  1. Stratum germinativum - basal layer
  2. Stratum spinosum - prickle layer
  3. Stratum granulosum - granular layer
  4. *Stratum lucidum - clear layer (only in palms)
  5. Stratum corneum - keratinized layer
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12
Q

Stratum Germinativum

A

First layer of Stratified Squamous Epithelium.
Basal layer. Rests on the basal lamina (which separates epithelium from connective tissue). Deepest layer. Contain nuclei. Highly mitotic layer. Melanocytes are found in this layer (they are derived from the CT). Cell shape is cuboidal to columnar. Basal surface forms hemidesmosomes (on the bottom) with tonofilaments. Lateral surfaces form desmosomes (lateral sides & top) with tonofilaments.

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13
Q

Stratum Spinosum

A

The second layer of Stratified Squamous Epithelium. Prickle layer. Polyhedral shape cells. Numerous short, blunt processes called intercellular bridges. Desmosomes & tonofilaments are formed on all surfaces. Some mitotic activity in the deepest portion of this layer. Melanocyte processes form.

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14
Q

Stratum Granulosum

A

The third layer of Stratified Squamous Epithelium. Granular layer. Flat diamond shaped. Keratohyalin granules form. Lamellated granules form, increase cell impermeability. Impermeable, can withstand shearing forces and mild acids & bases. Nuclei become spindle shaped, shrunken and pyknotic. Desmosomes and tonofilaments on all surfaces.

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15
Q

Stratum Lucidum

A

A layer of Stratified Squamous Epithelium. Clear layer. Only found in palms. May or may not be present. Found between granulosum and corneum. Thin, flat, few organelles, contains eleidin (altered keratohyalin).

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16
Q

Stratum Corneum

A

The fourth layer of Stratified Squamous Epithelium. Keratinized layer. Surface layer. No nuclei, cell is filled with keratin & melanin. Cells are called squames. Fourteen sided polygons, which interlock, increasing impermeability. Desmosomes and tonofilaments on lateral and inferior surfaces. Shedding of outer layer is called desquamate.

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17
Q

Cells

A
  • units of living substance (protoplasm)
  • contains cytoplasm & a nucleus
  • can exist individually or as part of a larger system
  • vary in size, shape, structure & function
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18
Q

Extracellular Substance (ES)/Intercellular Substance (ICS)

A
  • the product of living cells
  • distributed among the cells of the tissues
  • holds cells together
  • a medium for the passage of nutrients & waste from cell to capillary and vice versa
  • contains fibrous/formed elements and amorphous/ground substance
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19
Q

Fibrous/Formed Elements

A

a. Collagen (most abundant protein in body)
b. Reticulum
c. Elastin
d. Oxytalin

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20
Q

Amorphous/Ground Substance

A

A complex chemical substance (mucopolysaccharide)

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21
Q

Tissue Fluid (TF)

A
  • derived from the blood & lymphatic tissue
  • part of the blood plasma that diffuses through capillaries
  • is used as a vehicle for the transport of nutrients and waste
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22
Q

First Most Abundant Protein in the Body

A

Collagen

  • the major component in E.S. of all C.T.
  • a fibrous structural protein
  • most abundant protein in the body
  • product of a living cell, fibroblast (most abundant cell of C.T.)
  • example: dermis, tendons, ligaments, bone, alveolar, dentin, cementum, PDL, pulp
  • stays alive
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23
Q

Second Most Abundant Protein in the Body

A

Keratin

  • is a scleroprotein, the principle constituent of epithelium & horny tissues
  • second most abundant protein in the body
  • formed when epithelium cells die
  • example: epidermis, hair, nails, enamel
  • major component in epithelium: these cells start out alive then die
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24
Q

Ionic Theory

A

Nerve conduction via the sodium pump

a. Resting state with resting potential
b. Depolarization with action potential
c. Refractory period
d. Repolarization - restores resting potential

25
Q

Bilaminar Germ Disc

A

The blastocyte will become a BGD when two specific germ layers form

  • day 7-8 the embryoblast will form these two cell layers by a special arrangement of its cells
    1. Epiblast: top layer of cells
    2. Hypoblast: bottom layer of cells. Implantation & amniotic sac (day 6-11)
    3. Prochordal plate (day 14)
    4. Primitive groove (day 15)
    5. Primitive pit (day 15)
    6. Primitive streak (day 16)
    7. Primitive node/Hensen’s node (day 16)
26
Q

Trilaminar Germ Disc

A

Three germ layers from the embryo. Formation of the TGD occurs when the cells of the epiblast undergo active mitosis. These cells will migrate to the primitive streak and enter the primitive groove, then they pass between the epiblast and hypoblast layer, forming an intermediate layer - mesioderm.

  1. ectoderm layer: forms from existing epiblast
  2. mesoderm layer: formed by newly migrating epiblast cells
  3. endoderm layer: forms from mesoderm cells that replace the hypoblast (hypoblast is then pushed laterally into the yolk sac)
    * Neuroectoderm layer
27
Q

First Arch

A

Mandibular arch (“the big one”)
Major structures: maxilla (post 2/3), hard palate (post 2/3), mandible, tongue (ant 2/3)
**Muscles of Mastication: temporalis, masseter, medial & lateral pterygoid
**Cranial nerve: trigeminal (5th)

28
Q

Neural Plate

A
  • Forms when the notochordal process induces the cells of ectoderm to again proliferate
  • Cells give rise to a new cell layer called neuroectoderm
  • Neuroectoderm will form the flat neural plate
29
Q

Palate Development

A

Starts at week 6 and is completed by week 12

  • Secondary Palate (posterior 2/3rds): lateral palatine shelves fuse & form posterior 2/3rds of the palate/secondary palate (week 8)
  • Pre-maxilla/Primary Palate (anterior 1/3): forms from the intermaxillary process/globular process (inferior aspect). Lateral sides of the pre-maxilla fuse with the lateral palatine shelves and form primary palate. Palate formation is completed by the end of the third month.
  • Both the secondary palate and pre-maxilla fuse with the inferior aspect of the nasal septum
30
Q

Tongue Development (week 4 to week 8)

A

Develops from the 1st, 2nd & 3rd branchial arches (some from 4th). Starts forming in the floor of the pharynx.

  1. Anterior 2/3rds/Body: develops from 1st branchial arch as 3 swellings (lateral lingual swellings:two, tuberculum impar). All covered with ectoderm.
  2. Posterior 1/3rd/Root: develops primarily from 2nd & 3rd branchial arches and some of 4th. Forms the fourth lingual swelling or Hypobranchial Eminence (copula = 2,3,4 arches; epiglottic eminence = 4 arch).
31
Q

Fusion of Tongue (body & root)

A
  • sulcus terminalis: is formed by the fusion between the anterior 2/3rd & posterior 1/3rd of tongue
    - V shaped groove on posterior aspect of the tongue (apex post.)
  • foramen cecum: slight depression just posterior to the apex of the sulcus terminalis (origin of thyroid gland–>originates then migrates down the throat).
  • tongue is completed formed around week 8
32
Q

Dental Lamina/Primary Dental Lamina/Primary Epithelial Bands

A
  • form two horseshoe shaped bands, one in @ arch
  • gives rise to: tooth buds, enamel organs (enamel)
  • ectoderm epithelium
33
Q

Enamel Organ

A

Ectodermal tissue. Gives rise to enamel

a. Outer enamel epithelium: single layer of cells, convex outer layer
b. Inner enamel epithelium: single layer of cells, concave inner layer
c. Stellate reticulum: core cells, stellate shape (star shape)
d. *Enamel knot/Ahren’s knot: mass of SR cells
e. Enamel cord: string of cells from the knot
f. Enamel navel: surface depression where the enamel cord attaches
g. Cervical loop: gives rise to cervix of tooth–future CEJ, the root will eventually form from here.

34
Q

Stratum Intermedium

A

A stage of histodifferentiation of enamel organ–the second part of the Bell Stage.

  • appear during the bell stage
  • additional layer of flattened cells forming between the SR & IEE
  • will transport nutrients during the appositional stage to pre-ameloblasts
  • separates epithelium & CTs
35
Q

Origin of Permanent Molars

A

Part of histodifferentiation–second part of Bell Stage.

  • occurs via proliferation of the dental lamina
  • deciduous dental lamina will proliferate posteriorly before disintegrating
  • gives rise to dental lamina of the permanent molars (1st, 2nd & 3rd), and will form the tooth buds of these teeth.
36
Q

IEE

A

A part of histodifferentiation in enamel organ–second part of Bell Stage

  • change from squamous to tall columnar
  • organelles of IEE will elongate & polarize at end of bell stage
  • elongation starts in the center region & progresses to cervical loop/rim
  • IEE cells are now called pre-ameloblasts
  • enamel organ will form enamel
37
Q

Amelogenesis/Tome’s Process

A
  • short, blunt process formed by @ ameloblasts
  • contains only secretory & pinocytotic vesicles
  • occurs during Aprismatic Enamel (1st enamel to form) formation
38
Q

Aprismatic Enamel

A
  • occurs during induction of Amelogenesis
  • 1st enamel to form
  • forms in response to mantle dentin
39
Q

Enamel proteins

A

Ameloblasts/Ameloblastin: form the enamel matrix

40
Q

Reduced Enamel Epithelium (REE)

A
  • occurs during the Termination of Amelogenesis–before the root can form
  • cellular sheath that forms on formed enamel
  • fusion of the following layers: post-ameloblasts, stratum intermedium, and outer enamel epithelium.
41
Q

Nasmyth’s Membrane

A
  • primary enamel cuticle
  • secreted by post-ameloblasts
  • located between Reduced Enamel Epithelium & formed enamel
  • protective covering wears away after the tooth erupts
42
Q

Dental Papilla

A
  • stimulated by preameloblasts (epithelial)
  • increases in size
  • peripheral cells from squamous to tall columnar (responding to signaling molecules produced by pre-ameloblasts)
  • organelles of the dental papilla cells will elongate & polarize at the end of bell stage
  • peripheral cells are now called pre-odontoblasts (will eventually form dentin)
  • dental papilla will form the pulp
43
Q

Pre-odontoblasts

A

Formation: in the dental papilla
When: during histodifferentiation
From what: peripheral cells

44
Q

Circumpulpal Dentin

A
  • no Korff’s fibers
  • found in coronal & radicular dentin
  • forms all remaining dentin–the bulk of the tooth
45
Q

Dentin: organic vs. inorganic

A

70% of dentin is composed of inorganic material. Calcium hydroxyapatite is the main element. The organic component makes up 20% of dentin. It mainly consists of proteins: type I collagen (most common) and type V collagen.

46
Q

Peritubular Dentin

A

Forms dentin tubules, highly calcified.

47
Q

Intertubular dentin

A

Forms between the tubules, less calcified.

48
Q

Calcium hydroxyapatite

A

Sources:

  1. Mantle dentin
  2. Stratum intermedium

Part of the mineralization and selective resorption processes:

  • forms nidi of crystallization
  • released more & more as crystals grow in size until enamel matrix is fully mineralized
49
Q

Kroff’s Fibers Formation

A

Crown:
-only in mantle dentin between the odontoblasts
-short, thick course bundles of collagen fibers
-situated perpendicular to the DEJ (90 degree angle)
Root:
-arranged parallel to the CDJ (cementum-dentin junction?)

50
Q

HERS

A
  • Forms from cervical loop
  • Mitotic activity of OEE & IEE which grows downward
  • Two layers: outer-OEE, inner-IEE
  • Will grow inferiorly & will encompass the dental papilla
    Cell remnants: after HERS partially degenerates, it’s remnants form cell rests (cell rests of Malassez)
51
Q

Enamel Pearls

A
  • occurs when cementoblasts can’t pass through HERS (cell rests haven’t formed)
  • found at the CEJ & furcation areas
  • ameloblasts will form instead, from the IEE layers of HERS, producing enamel
    Anomaly:
    1. Not a true tumor
    2. Ectodermal disturbance
52
Q

Germination

A

Anteriors

  1. Forming tooth germ invaginates causing incomplete formation of two teeth
  2. Tooth has two crowns and one root
53
Q

Fusion

A

Anteriors

  1. Union of two normal separate tooth germs
  2. Caused by pressure or physical force producing contact between the tooth germs
  3. Complete: one large single tooth (one crown with one root)
  4. Incomplete: union of roots only (two crowns with one root)
54
Q

Concrescence

A

Anteriors

  1. A form of fusion
  2. Occurs after root formation is completed
  3. Causes: trauma or crowding, which results in roots contracting one another
  4. Roots are united by cementum only - two crowns with one large root
55
Q

Cleft Palate

A
  • Occurs during 3rd month of development
  • Origin: failure of pre-maxilla &/or the secondary palate to fuse to the nasal septum and/or failure of premaxilla to fuse with the secondary palate in the canine area
  • Most common in females
  • Tx: plastic surgery, ortho & speech therapy
56
Q

Cleft Lip

A
  • Occurs during the 2nd month of development
  • Caused by partial or complete failure of the globular process and the maxillary process to fuse
  • Most common in males
  • Unilateral or bilateral
  • Small to large void between the lateral border of the philtrum and the lip
57
Q

Tongue anomalies/defects

A
  1. Bifid tongue (rare): cleft in anterior 2/3rd of tongue, lateral lingual swellings fail to merge
  2. Microglossia (small): congenital defect; under development of musculature (rare)
  3. Macroglossia (large): congenital defect; over development of musculature, hypertrophy of musculature (common)
  4. Aglossia (absence of tongue): congenital defect involving 1st, 2nd and 3rd brachial arches (very rare)
  5. Ankyloglossia (very short lingual frenum): individual cannot lift tongue to roof of mouth (common)
58
Q

Treacher-Collins Syndrome

A

Mandibular Dysotosis
Origin: failure of neural crest cells of the head to migrate to the head and neck
Causes: malformation of the head and neck
Occurs during 2nd month of development
Hereditary
Appearance: bird/fish like shaped face, downward slant of eyelid fissures, absence or defect in lower eyelid, lack of eyelashes (esp lower), hypoplasia of facial bones (zygoma & mandible), malformation of external ear (also middle & inner ear), macrostomia: high vaulted palate (sometimes clefts); malocclusions, atypical hair (tongue shaped hair line), blind fistulas between angles of the ear and angles of the mouth

59
Q

Median Palatine Cyst

A

Lies on the line of fusion between the lateral palatine shelves of the maxillary process

60
Q

Median Mandibular Cyst

A

Lies on the lines of fusion of Mandibular processes (between centrals)

Histology & Embryology (1 decks)

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