CR1 KCP1 Cellular Adaptation

What are the three cell types based on their proliferative capacity?

Labile cells (continuously dividing), Stable cells (quiescent, can divide upon injury), and Permanent cells (unable to divide).

Give two examples of Labile cells.

Keratinocytes and intestinal epithelial cells.

Give two examples of Stable cells.

Hepatocytes and renal tubular epithelial cells.

Give two examples of Permanent cells.

Neurons and cardiac myocytes.

What molecules regulate transitions through cell cycle phases?

Cyclins and Cyclin-Dependent Kinases (CDKs).

What is checked at the G1/S cell cycle checkpoint?

Checks for DNA damage before allowing chromosome duplication in the S phase.

What is checked at the G2/M cell cycle checkpoint?

Checks for damaged or unduplicated DNA before the cell enters mitosis (M phase).

What causes reversible cell injury vs. irreversible cell injury?

Reversible injury is caused by mild, transient stimuli; Irreversible injury is caused by severe, progressive stimuli (including DNA damage).

What are two classic morphological signs of reversible cell injury?

Cellular swelling and fatty change.

What are the two forms of cell death resulting from irreversible injury?

Necrosis and Apoptosis.

Define Hypertrophy and state its cellular mechanism.

An increase in cell size (and organ size) due to increased production of cellular proteins and organelles without changing cell division rates.

Give one physiologic and one pathologic example of Hypertrophy.

Physiologic: Skeletal muscle enlargement in bodybuilders or pregnant uterus. Pathologic: Left ventricular hypertrophy from chronic hypertension or aortic stenosis.

Define Hyperplasia and state its cellular requirement.

An increase in the number of cells in an organ/tissue. Requirement: The cell population must be capable of dividing (labile or stable cells).

Give one physiologic and two pathologic examples of Hyperplasia.

Physiologic: Female breast at puberty/pregnancy or liver regeneration. Pathologic: Endometrial hyperplasia, Benign Prostatic Hyperplasia (BPH), or ductal epithelial hyperplasia.

Why is pathologic hyperplasia clinically significant?

It constitutes a fertile soil in which cancerous mutations may eventually arise.

Define Atrophy and name its two main molecular degradation pathways.

Reduction in cell size and number. Pathways: 1. Ubiquitin-proteasome pathway (protein degradation); 2. Autophagy (cell digests its own organelles).

List 6 causes of pathologic atrophy.

Decreased workload (disuse), loss of innervation, diminished blood supply, inadequate nutrition, loss of endocrine stimulation, and pressure/aging.

Define Metaplasia and state its mechanism.

Replacement of one adult cell type with another adult cell type. Mechanism: Reprogramming of tissue stem cells.

Describe respiratory tract metaplasia in smokers.

Ciliated columnar epithelium is replaced by stratified squamous epithelium to resist chronic smoke irritation.

Describe esophageal metaplasia in Barrett esophagus.

Stratified squamous epithelium is replaced by intestinal columnar epithelium due to chronic acid reflux.

Define Dysplasia and state its key histological features.

Disordered growth characterized by loss of cellular uniformity and loss of architectural orientation (principally in epithelia).

Is Dysplasia reversible or irreversible?

Mild to moderate dysplasia may be completely reversible if the stimulus is removed.

What is Carcinoma-in-situ?

Severe dysplastic changes involving the full thickness of the epithelium while remaining strictly confined by the basement membrane.

Define Dystrophy vs. Anaplasia.

Dystrophy: Degeneration/breakdown of tissue or organ. Anaplasia: Total loss of cellular differentiation (hallmark of cancer).

A 45-year-old woman with hypertension has a shrunken right kidney due to renal artery stenosis. What is the adaptive mechanism?

Atrophy caused by diminished blood supply (reduced oxygen and nutrients).