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Bioscience > The Tissues of the Human Body: Epithelia > Flashcards

The Tissues of the Human Body: Epithelia Flashcards

1
Q

CELL JUNCTIONS

Lateral junctions

A

Tight junction
Adherens junction
Gap junction
Desmosome

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2
Q

CELL JUNCTIONS

Basal junction

A

Hemidesmosome

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3
Q

Cytoskeleton

细胞骨架

A

Microfilaments e.g. ACTIN
微丝
bundles beneath cell membrane and cytoplasm; strength, alter cell shape; link cytoplasm to membrane; tie cells together; muscle contraction

Intermediate filaments e.g. KERATIN
中间纤丝
Strength;
move materials through the cytoplasm

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4
Q

TIGHT JUNCTIONS

A
  • Individual sealing strands transmembrane
  • More strands the tighter the junction
  • Many proteins involved but two key ones: claudins& occludins
  • Join the cytoskeletons of adjacent cells e.g. via ZO-1 to actin
  • Keep cell polarity by preventing migration of proteins between apical and basal surfaces
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5
Q

Tight junctions

A

Lots of these found in the stomach, intestines, bladder

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6
Q

ADHERENS JUNCTIONS

A
  • “Belt desmosome” or adhesion belts (zonula adherens) in some epithelial cells
  • Other cells are less continuous and are called “adhesion plaques”
  • More basal located than tight junctions
  • Have a plaque layer of proteins on the inside of the cell to join actin to cadherins
  • Cadherins(span the gap)
  • Cateninslink the Cadherinsto Actin(microfilament in cell cytoplasm)
  • Adherens junctions prevent cell separation from tension forces like in contractions
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7
Q

DESMOSOME JUNCTIONS

细胞桥粒连接

A
  • Lateral wall
  • Have “plaque” just like adherens junctions
  • Resist shearing forces
  • Example: they bind muscle cells
  • Cadherinspans the gap
  • BUT link cell surface to Keratin(a cytoskeletal intermediate filament)
  • Keratin spans from one desmosome to another on the other side of the cell – structural integrity
  • Most common in skin epithelium and cardiac cells of the heart to prevent pulling apart
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8
Q

GAP JUNCTIONS

间隙连接

A
  • Direct connection between cells
  • 6 connexin联接蛋白 protein molecules form connexion连接 or hemichannel半通道
  • 2 hemichannels make up gap junction
  • Allow ~1kDa molecules through
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9
Q

Hemidesmosome

半桥粒

A
  • Connect epithelia to the basement membrane
  • Links cellular basal intermediate filament(Keratin) to the basement membrane
  • Hemidesmosome –(INTEGRINlinker protein (instead of cadherin) binds to LAMININin the BM and to Keratinintermediate filament in the cytoplasm)
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10
Q

The Basement Membrane

A 
All epithelia overlay a basement membrane composed of two parts:
BASAL LAMINA(secreted by the epithelial cells) containing collagen, laminin, other proteoglycans, glycoproteins, etc
RETICULAR LAMINA(produced by cells of the underlying connective tissue known as fibroblasts) containing fibrous proteins such as fibronectin, collagen etc
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11
Q

Functions of the Basement Membrane

A

Supports the overlying epithelium

Provides a surface along which epithelial cells migrate during growth and wound healing

Acts as a physical barrier

Participates in the filtration of substances in the kidney

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12
Q

The basement membrane can act as a barrier to invasion by malignant melanoma.

A

Once the barrier has been penetrated, the chances of metastasis(spread) occurring increase.

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13
Q

There are TWO types of Epithelial tissue

A

Covering and Lining Epithelia

Glandular Epithelia

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14
Q

Covering and Lining Epithelia

a. ARRANGEMENT

A

i. Simple: single layer (secretion; absorption; filtration)
ii. Stratified: two or more layers (protective)
iii. Pseudostratified: appears to have multiple layers as judged by positions of nuclei.

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15
Q

Covering and Lining Epithelia

b. SHAPE

A

i. Squamous: flat and thin (helps allow passage by diffusion)
ii. Cuboidal: about as tall as they are wide (secretion; absorption)
iii. Columnar: more tall than wide (secretion; absorption)
iv. Transitional: a stratified epithelium in which the cells can change shape from cuboidal to flat shape depending on organ shape (allow stretch e.g. urinary bladder)

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16
Q

Covering and Lining Epithelia

A 
Simple squamous*
Simple cuboidal*
Simple columnar* 
Stratified squamous*
Stratified cuboidal 
Stratified columnar
Transitional 
Pseudostratified columnar*
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17
Q

Simple Squamous鳞状的 Epithelium

Features

A

Features

  • Most delicate epithelium
  • Where there is filtration (kidney); diffusion (lung); secretion where slippery surface needed (e.g. outer layer of serous membranes);
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18
Q

Simple Squamous Epithelium

Appearance

A

Appearance

  • Thin flat and somewhat irregular like a jigsaw
  • Cells are “like fried eggs” or paving stones
19
Q

Simple Squamous Epithelium

Specialised Subtypes

A

Specialised Subtypes

  • Mesotheliumlines pericardial, pleural, peritoneal cavities
  • Endotheliumlines inside of heart and blood and lymphatic vessels
20
Q

Simple Squamous Epithelium

Location examples:

A

Location examples:

In Bowman’s capsule of the kidney, lines cardiovascular and lymphatic systems, inside the eye, alveoli of lungs, visceral cavity linings, inside blood vessels and inside the heart

21
Q

Simple Cuboidal立方形的 Epithelium

A

Features

Where there are SECRETION and ABSORPTION

22
Q

Simple Cuboidal Epithelium

A

Appearance

  • Cuboidal or hexagonal boxes.
  • The distance between adjacent nuclei is approx. the height of the epithelium
23
Q

Simple Cuboidal Epithelium

A

Specialised Subtypes

Nil

24
Q

Simple Cuboidal Epithelium

A

Location examples:

pancreas ducts; parts of kidney tubules, smaller ducts of many glands; secretory chambers of thyroid; the anterior surface of the lens; pigmented epithelium at posterior of the retina; secretory part of some glands like the thyroid

25
Q

Simple Columnar柱状的 Epithelium

A

Features

More cytoplasm so more organelles

26
Q

Simple Columnar Epithelium

Come in two major subtypes

A

i.Non-ciliated simple columnar epithelium.

Ciliated simple columnar epithelium

27
Q

Simple Columnar Epithelium

A

Appearance

  • Rectangular
  • Often hexagonal but taller and more slender than cuboidal
  • Nuclei often elongated and near the base of the cell
  • Height of cell is several times the distance between adjacent nuclei
28
Q

Simple Columnar Epithelium

A

Specialised Subtypes

Simple columnar epithelium can have:cilia or microvilli

29
Q

Non-Ciliated Simple Columnar Epithelium

A

Features
•Single layer
•Microvilli on the apical surface
•Have goblet cells interspersed

30
Q

Location examples of non-ciliated columnar epithelium:

A

Examples: lines gut mucosa from the stomach to anus; ducts of many glands; gall bladder.

Function: secretion and lubrication (mucus goblet cells); absorption;

31
Q

Ciliated Simple Columnar Epithelium (move materials)

A

Features
•Single layer
•Have goblet cells as well

32
Q

Ciliated Simple Columnar Epithelium (move materials)

A

Location examples:

Examples: some bronchioles, uterine fallopian tubes, sinuses; central canal of the spinal cord, ventricles of the brain
Function: synchronous movement assists motility of mucus and foreign objects or oocytes

33
Q

Stratified Squamous Epithelium

A

Features

  • Located where mechanical or chemical stresses are severe严重的
  • All forms protect against microbes微生物
  • In some places where mechanical stress and dehydration major issue apical顶端 cells are packed with keratin角蛋白 – makes the surface tough and waterproof防水.
34
Q

Stratified Squamous Epithelium

A

Appearance

  • Cells form layers like plywood夹板 or pancakes in upper layers
  • Lower layers may be cuboidal立方形的 or columnar柱状
  • Cells furthest最远的 from nutrition is thinner and less active.
35
Q

Stratified Squamous Epithelium

A

Specialised Subtypes

  • Keratinised 角质化的
  • Non-keratinised
36
Q

Stratified Squamous Epithelium

A

Location examples:

  • Keratinised: skin
  • Non-keratinised: mouth, throat, tongue, oesophagus食管, anus, and vagina
37
Q

Stratified Squamous Epithelium (non-keratinized)

A

Examples:

mouth, throat, tongue, oesophagus, anus, and vagina

Function:

protection from abrasion擦伤, defence from microbes, require secretions from glands

38
Q

Psuedo伪-stratified分层 Columnar Epithelium柱状上皮

A

Features

  • All cells contact BM but not all reach the apical surface of the tissue
  • Actually a simple epithelium
39
Q

Psuedo-stratified Columnar Epithelium

A

Appearance

  • Nuclei at all different levels
  • Appears to have several layers but it is not actually the case
40
Q

Psuedo-stratified Columnar Epithelium

A

Specialised Subtypes

i)Pseudo-stratified ciliated有纤毛的 columnar epithelium

  1. )Cilia on some cells
  2. )Secrete mucus (from goblet cells)

ii)Pseudo-stratified non-ciliated columnar epithelium

  1. )No cilia
  2. )Lack goblet cells
41
Q

Glandular腺的 Epithelia

A

Glands consist of a single cell or a group of cells that secrete substances into ducts导管, onto a surface or into the blood.

42
Q

Endocrine gland

内分泌腺

A

Secrete directly into blood usually via traversing interstitial fluid通过穿越组织液

Example

Pituitary脑垂体
pineal松果体
thyroid 甲状腺
parathyroid甲状旁腺

43
Q

Exocrine gland

外分泌腺

A

Secrete into ducts that empty onto the surface of a covering or lining epithelium.

Example

Sweat and salivary glands汗腺和唾液腺
oil glands脂腺
wax glands蜡腺
pancreas胰腺

Bioscience (12 decks)

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