Chapter 1.1 Growth Adaptations Flashcards
What will cause growth adaptations in an organ?
increase, decrease or change in stress on organ can result in growth adaptations
organ is in homeostasis with the physiological stress placed on it
Describe what will cause hypertrophy and hyperplasia and define both.
increase in stress leads to increase in organ size (if organ has to do more work, will become bigger to do that extra work)
increase in size = hypertrophy
increase in number of cells =hyperplasia
What is the mechanism that underlies hypertrophy?
cell- make it bigger
to increase cell size, cytoskeleton of cell (gives cell size and shape) so must increase production of cytoskeleton which is predominately made of protein
so involves gene activation and protein synthesis, also must produce organelles (increase mitochondria if we increase its size)
What is the mechanism that underlies hyperplasia?
involves production of new cells from stem cells
Give an example of how hyperplasia and hypertrophy occur together.
uterus during pregnancy
smooth muscle of uterus undergoes hyperplasia …more cells produced, and hypertrophy…cells become bigger
When might a tissue undergo hypertrophy only?
permanent cells cannot make new cells so undergo hypertrophy only
permanent tissues: (cardiac myocytes, skeletal muscle, neurons)
By what mechanism might the wall of the left ventricle grow in size?
hypertrophy bc the muscle of the heart cannot undergo hyperplasia
What can pathologic hyperplasia progress to? Give an example and an exception.
dysplasia and cancer
(ex of physiological hyperplasia =pregnancy…no increased risk for cancer)
ex: endometrial hyperplasia (endometrium grows with exposure to estrogen and it develops and sheds with exposure to progesterone, prolonged exposure of estrogen can progress to endometrial hyperplasia and then endometrial carcinoma)
note: obesity can increase levels of estrogen
exception: begin prostatic hyperplasia (is pathologic but is not related to cancer)
What will induce atrophy of an organ?
decrease in stress leads to a decrease in organ size
decrease in the size and number of cells
Describe the mechanism of atrophy.
decrease in cell number - occurs via apoptosis
decrease in cell size occurs via
- ubiquitin-proteasome degradation of cytoskeleton (proteasome recognizes ubiquitin tagged proteins and destroys them)
- autophagy of cellular compartments, cell consumes its own contents in vaccules then destroys them in lysosomes (require less organelles in cell bc shrinking cell size)
What is metaplasia?
Give a classic example.
If stress on organ CHANGES, then organ will respond by changing its cell type
metaplasia most commonly involves surface epithelium (cells that line body surfaces)
-the new cells better able to handle the change in stress
Barrett esophagus- (lined by squamous epithelium), sharp demarcation between esophagus and stomach, stomach lined by columnar epithelium, if acid refluxes from stomach up into lower esophagus will result in change in stress in lower portion of esophagus (presence of acid in lower portion of esophagus will result in change from squamous to columnar non-ciliated mucinous epithelium) …columnar much better suited to handle acid
What are 3 types of epithelium?
squamous epithelium (keratinizing or nonkeratinizing)
columnar (a lot of gut)
transitional or urothelium (lines the urinary tract)
What is the mechanism by which metaplasia occurs?
reprogramming of stem cells
SC present in lower 1/3 of esophagus which have ability to produce new squamous cells, in presence of acid they convert to columnar cells
reversible with the removal of the driving stressor
Ex: treatment of GERD
Is metaplasia reversible?
reversible with the removal of the driving stressor
Ex: treatment of GERD
Given an example of how metaplasia can progress to dysplasia and cancer. What is an important exception?
Ex: Barrett esophagus
risk factor for adenocarcinoma of esophagus
Exception: Apocrine metaplasia (one of changes seen in association with fibrocystic change of breast)
What type of deficiency can result in metaplasia? Give an example.
Vitamin A deficiency
(increased risk for night blindness w Vitamin A deficiency)
Vitamin A necessary for maintenance of specialized epithelia in the body, (the conjunctiva of the eye- highly specialized squamous epithelium which requires Vitamin A to remain in that state)
Ex: keratomalacia
Describe the mechanism by which a Vitamin A deficiency can affect the immune system.
Vitamin A deficient patients can become deficient in immune system bc Vitamin A necessary for maturation of cells of immune system
when patients get 15/17 translocation they develop disease called acute promyocytic anemia…the 15/17 translocation involves retinoic acid receptor. translocation disrupts Vitamin A receptor and causes cells to remain in blast state, accumulate and result in promyoytic anemia.
What are some examples of mesenchymal tissues?
Describe an example of how mesenchymal tissues can undergo metaplasia.
bone, blood vessel, fat, cartilage, =connective tissues
can undergo metaplasia
ex: myositis ossificans
(inflammation of the skeletal muscle results in metaplastic production of bone in skeletal muscle) …usually due to trauma to skeletal muscle, inflammation, as part of healing skeletal muscle converts to bone
What does dysplasia result in? Define the term and provide an example.
disordered cell growth
proliferation of precancerous cells (CIN=cervix)
CINI CINII CINIII (CIN is actually dysplasia)
results from longstanding pathologic hyperplasia (endometrial hyperplasia) or metaplasia (Barrett’s esophagus)
Is dysplasia reversible?
dysplasia is reversible with alleviation of inciting stress
(can treat GERD and dysplasia)
(if stress persists and it progresses to carcinoma- irreversible)
Define aplasia and give an example.
aplasia
without growth = failure of cell growth or organ growth during embryogenesis
ex: unilateral renal agenesis (failure to develop 1 kidney during embryogenesis)
Define hypoplasia and give a clinical example.
decrease in cell production during embryogenesis
results in relatively small organ
streak ovary in Turner syndrome
