Principles of Organization of Organs- Histology Flashcards

1
Q

What are ‘hollow’ organs?

A

These are the body tubes that connect with the outside of the body (the digestive, respiratory, and urogenital tracts)

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2
Q

Hollow organs are all lined by what?

A

a mucosa or mucus membrane

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3
Q

What do mucous membranes consist of?

A

consists of the surface epithelium, the underlying connective tissue (called the lamina propria).

NOTE: In the GI tract, there is also a layer of smooth muscle, which is called the muscularis mucosa.

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4
Q

T or F. Muscularis externa lies external to the mucosa in the GI tract

A

T

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5
Q

What does muscularis externa consist of?

A

1-3 layers of smooth muscle. (typically 2 in GI tract)

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6
Q

External to muscularis externa in hollow organs is what?

A

loose connective tissue.

For organs not situated within a body cavity, the outer layer outside the connective tissue is called the adventitia and attaches the organ to adjacent structures.

For organs situated within a body cavity, this connective tissue is covered by mesothelium (i.e. simple squamous epithelium); together they are called the serosa.

Some organs have an additional layer of connective tissue between lamina propria & muscularis externa, which is termed the submucosa.

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7
Q

a collection of tissues joined in a structural unit to perform a common function is called what?

A

an organ

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8
Q

What are three main architectural types of organs?

A

hollow (tubular)
glands
solid

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9
Q

Name 5 examples of tubular organs

A
  • Digestive tract – esophagus, stomach, small intestine, large intestine
  • Respiratory tract – trachea, bronchi, bronchioles
  • Urinary tract – ureters, urinary bladder, urethra
  • Female reproductive tract – oviduct, uterus, cervix, vagina
  • Male reproductive tract – ductus deferens, urethra
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10
Q

What are the four layers of most hollow organs? Note that some others have additional layers

A

epithelium
lamina propria
muscularis externa
adventitia or serosa

Note that some others have additional layers

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11
Q

What is mucosa?

A

the lining of the body tubes that connect with the outside of the body (i.e. digestive, respiratory, and urogenital tracts).

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12
Q

What two layers make up the mucosa?

A

epithelium and lamina propia (term used for the underlying connective tissue)

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13
Q

Some organs have an additional submucosa layer. Where is this layer?

A

between lamina propia and muscular external

it is connective tissue

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14
Q

T or F. All hollow organs have muscularis externa

A

T

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15
Q

T or F. All hollow organs have muscularis mucosa

A

F. Only present in the GI tract

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16
Q

For organs situated within a body cavity, this outer layer is comprised of loose connective tissue covered by mesothelium (i.e. simple squamous epithelium). What is this layer called?

A

serosa

Adventitia – for organs not situated within a body cavity, the outer layer is made up of connective tissue that attaches the organ to adjacent structures.

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17
Q

In the GI, the muscular externa typically exists as how many layers? What are those layers?

A

2 layers

inner circular and outer longitudinal

NOTE: can exist as 1,2, or 3 layers

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18
Q

contraction of circularly-arranged muscle in the GI results in what?

A

narrowing of the lumen

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19
Q

contraction of longitudinally-arranged muscle in the GI results in what?

A

shortening of the tube

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20
Q

In the GI tract, contraction of smooth muscle is controlled by what?

A

Post-synaptic sympathetic fibers & parasympathetic ganglion neurons present and modulate the contraction of smooth muscle

21
Q

What kind of neurons modulate smooth muscle contraction in the GI tract?

A

enteric neurons

22
Q

Where are enteric neurons typically found in the GI tract?

A

typically grouped in small clusters, mostly in submucosa and between smooth muscle layers of muscularis externa.

23
Q

the submocusa contains of what kind of tissue?

A

dense irregular CT

Sometimes contains glands – e.g. esophagus, duodenum, trachea

24
Q

What are the layers of mucosa?

A

epithelium
lamina propria
(also muscularis mucosa in GI tract)

25
Q

T or F. Mucosa varies extensively in different organs

A

T.

Differences in:
architecture – presence of folds, projections, and/or invaginations

cellular composition – types of cells present & variations in their relative abundance

26
Q

What kind of epithelium is present in the esophagus?

A

stratified squamous non-keratinized

27
Q

What kind of epithelium is present in the trachea?

A

pseudostratified ciliated columnar

28
Q

What kind of epithelium is present in the urinary bladder?

A

transitional

29
Q

What kind of epithelium is present in the stomach, small intestine, and large intestine?

A

all are simple columnar, but differences in the cell types present and their relative abundance

30
Q

What is Celiac disease?

A

immune reaction to gluten; inflammation & shortening of microvilli & villi, with their eventual loss

31
Q

What is Crohn’s disease?

A

chronic inflammation of uncertain etiology, perhaps autoimmunity

32
Q

What is epithelial metaplasia?

A

Adaptive response whereby original type of epithelial cells is replaced by a type more resistant to chronic inflammation, environmental conditions, stress, etc

Epithelial stem cells change their patterns of gene expression.

33
Q

What is the most common epithelial cell type ‘change’ as part of epithelial metaplasia?

A

columnar to stratified squamous

  • in trachea & bronchi, in response to prolonged exposure to cigarette smoke
  • in cervix, associated with chronic infections
    If not reversed (e.g. by removing pathogenic stimulus), cells can become cancerous
34
Q

What other type of transition of cell type can occur as part of epithelial metaplasia?

A

‘Squamous-to-columnar’ transformation can also occur

35
Q

What is Barrett’s esophagus?

A

lower part of esophagus transforms into intestinal-like epithelium after repeated exposure to stomach acid.

36
Q

How do glands form?

A

Form by invagination of an epithelium

37
Q

Notes on the route of endocrine glands from epithelium to bloodstream

A

Secretory product -> diffuses into nearby connective tissue -> enters the bloodstream

38
Q

What are the mechanisms of secretion of exocrine glands?

A

merocrine
apocrine
holocrine

39
Q

Describe merocrine secretion

A

exocytosis from membrane-bounded vesicles
most exocrine glands are merocrine
e.g. salivary glands and pancreas
the term ‘eccrine’ refers specifically to merocrine sweat glands

40
Q

Describe apocrine secretion

A

apical part of cell pinches off, releasing lipid droplet e.g. milk from mammary gland

41
Q

Describe apocrine secretion

A

secretory product is released as cell dies & disintegrates e.g. sebaceous glands of hair follicle

42
Q

What are the two types of organization of exocrine glands?

A

tubular or acinar/alveolar

simple or compound

43
Q

What are some examples of solid organs?

A

liver
kidneys
ovaries
endocrine glands – e.g. adrenal, pituitary
exocrine glands – e.g. salivary glands
pancreas – has both endocrine and exocrine glandular components lymphoid organs – e.g. lymph node, spleen

44
Q

What are the types of organization of solid organs?

A

lobes and lobules

cortex and medulla

45
Q

What kinds of organs have a cortex/medulla organization?

A

kidney, lymph nodes, adrenal gland, ovary

46
Q

What kinds of organs have lobes and lobules?

A

liver, pancreas, many glands

47
Q

What is the parenchyma?

A

functional part of an organ

48
Q

What makes up the parenchyma in the Liver, kidney, pancreas, and various glands?

A

epithelial cells

49
Q

What makes up the parenchyma in lymphoid organs?

A

lymphocytes