Lecture 6: Cell Adaptation

Question 1

What is the definition of hyperplasia?

Answer 1

Hyperplasia is the increase in number of cells

Question 2

What are the two types of Hyperplasia?

What are the two causes of hyperplasia?

Answer 2

Two types of hyperplasia: Nodular or cystic

Two causes of hyperplasia: Physiologic and pathologic

Question 3

What are some characteristics of physiologic hyperplasia?

Answer 3

Physiologic hyperplasia

• Often a response to hormones
• Often compensatory
• May be regenerative, acting to repair a site

Question 4

What are some characteristics of pathologic hyperplasia?

Answer 4

Pathologic hyperplasia:

• Due to Inappropriate or excessive hormones (ACTH -> Adrenal cortex)
• Due to Irritation
• Unknown/idiopathic cause

Question 5

What organs are commonly affected by hyperplasia?

Answer 5

Common examples:

• Liver
• Spleen
• Pancreas
• Lymph node/spleen

Very common example: Cystic endometrial hyperplasia

Question 6

Why do we care about hyperplasia?

Answer 6

Why do we care?

We need to know what the cause is. What is this in response to?

Also, possibly preneoplastic.

Question 7

Hyperplasia vs neoplasia?

Answer 7

Hyperplasia:

• Controlled growth, normal process
• Reversible, if the inciting cause is determined and removed
• The cause is known.

Neoplasia:

• May be harder to recognized the cause, may not see a justification for an increase in cell number.
• Unregulated, unorganized.
• May not be reversible, if it’s a genetic change

Question 8

Is hypertrophy cell swelling?

Answer 8

No, hypertrophy is an increase in the size of cells or organ.

This is not cell swelling.

Cells swell because they are taking on water, or lipids. The cells got very big, but it’s not because they were able to do more a job. They were very fragile.

Question 9

Why does hypertrophy happen?

Answer 9

Hypertrophy is an increase in the size of cells or organ, due to the increase in volume of organelles. The increase in organelles leads to an overall increase in cell size.

Question 10

What are the two types of hypertrophy?

Answer 10

Two types of hypertropy are physiologic or compensatory.

In response to work/increased demand

Question 11

What types of cells can’t undergo hyperplasia?

Answer 11

“Permanent” cells, like neurons or myocardiocytes. These cells don’t regenerate, so they can’t become hyperplastic.

They could potentially become hypertrophic.

Question 12

When labile cells (skin, GI, respiratory, or hematopoietic) become hyperplastic, what are they typically working to do?

Answer 12

When labile cells become hyperplastic, they are typically working to repair something.

(From review session, not from lecture)

Question 13

When a stable cell type (glandular, liver, kidney, or endocrine) undergoes hyperplasia, what type of hyperplasia will that typically be?

Answer 13

The hyperplasia of stable cell types typically results in nodular hyperplasia.

(from review session, not lecture)

Question 14

How would you describe the circled kidney?

Answer 14

The circled kidney is a hypoplastic kidney.

The contralateral kidney had more work to do, so it increased in size as an organ to handle the increased workload

Sometimes we see this change in a cat/animal that has no renal abnormalities in the bloodwork at all

Can be an incidental finding

Question 15

What’s happening in this image?

Answer 15

This is hypertrophic cardiomyopathy.

For reasons we don’t always understand, the myocardium of the left ventricle becomes very large, due to the increased size of the myofibers. The cats can be asymptomatic until you go to do a dental, or spay.

We don’t have a good antemortem test at this time.

Question 16

What is an example of both hypertrophy and hyperplasia?

Answer 16

Prostatomegaly would be an example of this.

The entire size of the organ may increase. There would be an increase in cell size and cell number.

Question 17

Metaplasia is when one adult cell type is replaced by another adult cell type of the same ________ _______,

Answer 17

Metaplasia is when one adult cell type is replaced by another adult cell type of the same germ line.

So, an epithelial cell wouldn’t be replaced with a lymphocyte, for example.

Question 18

What are two broad categories through which metaplasia can be induced?

What are some examples of each?

Answer 18

Metaplasia can be:

• induced (due to increases in estrogen, or a vitamin A def.)
• caused by irritation (in the trachea of a smoker, normal ciliated columnar cells become stratified squamous epi)

Question 19

When you have metaplasia in epithelial tissue, what are some pros/cons to it?

Answer 19

**It’s protective. ** Great for skin, not great for trachea, other organs that interface with the environment

Loss of cilia, loss of clearance

When you lose a special feature of those cells, like cilia, then you’re also losing an important clearance mechanism for the resp. tract

Can be preneoplastic

Question 20

What are some characteristics of metaplasia in mesenchymal tissue?

Answer 20

Mesenchymal tissue = connective tissue

Mesenchymal metaplasia may indicate:

• An altered cellular environment (May be hormonal, may be constant mechanical trauma)
• Decreased or increased oxygen in the tissue
• Example? Osseous metaplasia.

Osseous metaplasia? In the face of chronic stress and perhaps overexposure to corticosteroids, one skin lesion that can occur is the formation of bone within skin. Hematopoetic cells in the bone marrow, of bone that shouldn’t be there in the first place!! Common in oral masses in dogs.

Question 21

What the significance of metaplasia?

Answer 21

Metaplasia may be:

Reversible, if the inciting cause is removed

May be protective or harmful

May be a preneoplastic lesion, like a carcinoma in situ.

Question 22

An organ that is enlarged due to an increased number of cells is:

a. Hyperplastic
b. Hypertrophic
c. Metaplastic

Answer 22

An organ that is enlarged due to an increased number of cells is:

a. Hyperplastic

b. Hypertrophic
c. Metaplastic

Question 23

What is atrophy?

Answer 23

Atrophy is the decrease in cell size or number of cells, tissue, or organ after normal growth has been reached.

The key feature is that the cell has to have reached its normal size at some point, and then gotten smaller

Question 24

What are some types of atrophy, by mechanism?

i.e. what’s a mechanical reason why a cell would atrophy?

Answer 24

Types of atrophy, by mechanism:

• Disuse
• Denervation
• Pressure - decreased blood flow due to a decrease in oxygen or nutrients
• Reduced work load
• Decreased hormones
• Any reduction in nutrition/oxygen
• Aging/senility

Question 25

What are the morphologic types of atrophy?

Answer 25

Types of atrophy, by morphology:

• Simple atrophy
• Fatty atrophy
• Fibrous atrophy
• Serous atrophy

Question 26

What is fatty atrophy?

Answer 26

Fatty atrophy is fat replacement in connective tissue. Adipocytes replace myofibers.

Question 27

What is fibrous atrophy?

Answer 27

Fibrous atrophy is when something is decreasing in size, and there’s fibrous replacement

Increased fibrous tissue within connective tissue.

(She literally said “something” in lecture and didn’t elaborate on what, so…..)

Question 28

Atrophy vs. involution? Discuss.

Answer 28

Atrophy is the decrease in cell size or number of cells, tissue, or organ after normal growth has been reached. The term “atrophy” implies an adverse situation/environment.

Involution is the reduction in cell number without degeneration. Involution in a normal physiologic process that involves apoptosis. Examples: How the thymus involutes with age, or how the uterus shrinks/involutes after birth.

Question 29

What do you need to ask yourself when you see atrophy?

Answer 29

Presence of atrophy? Ask yourself:

Where is this happening?

What exactly is happening?

Are there any indicators of disease?

Question 30

What are some potential fates of atrophic tissues?

Answer 30

Atophy could:

• Be reversible. For example, muscle atrophy in a broken limb
• Persist, as it is
• Progress into serious bad news, like fat (serous) atrophy or fibrosis atrophy

Question 31

What type of atrophy is the brain on the right undergoing?

Answer 31

Pressure atrophy.

Dog brain, blockage of CSF in one of the ventricles. Result: Severe hydrocephalus. Remaining cerebrum collapsed on itself.

Question 32

What is the gross morphology of atrophy?

Answer 32

Grossly, you’ll see a decrease in the weight and volume of the organ.

Loose covering

Tortuous vessels (over the surface of the organ. What used to be fully expanded, has collapsed)

Firm +/- fatty

Question 33

What is the microscopic morphology of atrophy?

Answer 33

Microscopically, you’ll see either a decrease in the number of cells, a decrease in the cell sizes, or potentially both.

Question 34

What is the EM morphology of atrophy?

Answer 34

EM morphology of atrophy?

Decreased organelles: Less ER, fewer mitochondria, less intracellular filaments

Increased autophagocytic vacuoles, lipofuscin

Question 35

What are the last fat stores, that atrophy in serous atrophy of fat?

Answer 35

Last fat stores:

Perirenal

Epicardial

Bone marrow

Question 36

Why do we care about serous atrophy of fat?

Answer 36

Important to recognize because it implies a severe caloric deficiency

When we see an animal that’s thin, we know that there’s been a severe lack of nutrients if we see a lack of fat around the heart and the kidneys

If there’s been a rapid decrease in availability of food, then we see serous atrophy of fat, when those fat stores are gone so rapidly that the remaining stroma around it is filled in with clear, gelatinous fluid

If you shake it back and forth, you’ll see what used to be fat is instead clear, pale yellow, very fragile substance

Would see there anywhere we would expect to see fat, esp. around the heart and the kidneys

Not uncommon for animals. Perhaps not always in an intentional or malicious way, but people may not feed adequately.

Upon necropsy, may not able to prove intent, but you can prove that the animal was severely malnourished.

This can NOT occur postmortem

Question 37

What does lipofuscin represent, in a cell?

Answer 37

Lipofuscin is essentially the break down product of chronic cell stress

Long term phagocytosis

May see it in a cell, but it doesn’t indicate why the cell was stressed.

Called a “wear and tear” pigment for that reason

Question 38

There are a lot of Cellular Adaptation images at the end of the lecture that were too big to put on here. Look through them!

Answer 38

You are a champion!