Chapter 1 Flashcards
Hypertrophy = bigger cells, hyperplasia= more cells: Both are responses to cellular stress
How does hypertrophy occur?
gene activation, protein synthesis, and production of organelles
NOTE: Hypertrophy and hyperplasia typicall occur together
What tissues can only undergo hypertrophy (not hyperplasia)?
Cardiac muscle, skeletal muscle, and nerve
Note that pathologic hyperplasia (e.g. endometrial hyperplasia) can progress to dysplasia and eventually cancer. What is an exception?
BPH doesnt increase risk for prostate cancer
Overview of atrophy
Decreases ins tress cause a decrease in cell number via apoptosis and a decrease in cell size via ubiquitin-proteosome degradation of the cytoskeleton and autophagy of cellular components (intermediate filaments are tagged with ubiquitin and destroyed by proteosomes)
Metaplasia= changing of cell type to another (e.g. Barrett’s Esophagus). What is the change in BE?
nonkeratinizing squamous to noncilitaed columnar
Remember that metaplasia is generally reversible with removal of the driving force (i.e. with GERD) BUT persistent metaplasia can progress to dysplasia (I.e. Barretts to adenocarcinoma; exception- apocrine metaplasia of the breast has no increased risk for cancer)
What else can cause metaplasia?
Vit A deficiency (VitA is needed for differentiation of specialized epithelial surface suchs as the conjuctiva covering the eye and in deficiency, the goblet cell/columnar epithelium of the conjunctiva undergoes metaplasia into keratinizing squamous epithelium)
Mesenchymal tissue can also undergo metaplasia as in myositis ossificans in which CT within muscle changes to bone during healing after trauam
Dysplasia often refers to proliferation of precancerous cells (e.g. CIN is dysplastic and can lead to cervical cancer)- often arises from longstanding metaplasia or hyperplasia
NOTE: Dysplasia is typially reversible
What is aplasia?
Failure of cell production in utero (whereas hypoplasia is a decrease in cell production in utero, resulting in a small organ)
When cells are highly susceptible in injury?
Neurons (whereas skeletal muscle is more resistant)
NOTE: Slow developing ischemia (i.e. renal artery stneosis) results in atrophy while acute ischemia (e.g. renal artery embolus) causes cell injury
What are some common causes of cellular injury?
inflammation, nutritional deficiency or excess, hypoxia, trauma, and mutations
What is hypoxia?
Low oxygen delivery to tissue (low O2= cant make ATP= cell injury)
Common causes of ischemia (decreased blood flow through an organ)?
decreased arterial perfuison (e.g. atherosclerosis)
decreased venous drainage (e.g. Budd Chiari)
shock
What is hypoxemia?
low partial pressure of oxygen in the blood (Pao2 less than 60 mm Hg, SaO2 less than 90%)
Common causes of hypoxemia?
- High altitue
- hypoventilation
- diffusion defect (e.g. interstital pulmonary fibrosis)
- V/Q mismatch (blood bypasses oxygenated lung due to shunt, etc. or oxygenated air cannot reach blood due to ventilation problems such as atelectasis)
Left ventricular hypertrophy
Dilated cardiomyopathy
Decreased O2 carrying capacity arises with Hb loss or dysfunction. Examples include:
- Anemia (decrease in RBC mass)- Pao2 and Sao2 normal
- CO poisoning (Pao2 normal but SaO2 decreased)
- Methamoglobinemia
How does CO poisoning appear clinically?
What is Methamoglobinemia?
When the iron in heme is oxidized to Fe3+ and cannot bind oxygen (Pao2 normal and Sao2 decreased)
-seen with oxidant stress (e.g. sulfa or nitrate drugs) or in newborns
How does Methamoglobinemia present?
cyanosis with chocolate colored blood
How is Methamoglobinemia tx?
IV methylene blue with helps reduce iron back to Fe2+
What cellular processes occur as a result of low ATP?
1- NaK pumps stop resulting in sodium and water buildup in the cell
- Ca2+ pumps fail resulting in Ca2+ buildup in the cytosol
- Switch to Anaerobic glycolysis. lactic acid builds up results in acidosis, whch denatures proteins and precipitates DNA
The hallmark of REVERSIBLE cellular injury is _________
cellular swelling - the cytosol swells resulting in loss of microvilli and membrane budding