DISTURBANCE OF GROWTH
Distrubances of growth are divided into three main groups:
1- Disorders leading to diminished growth e.g. atrophy.
Atrophy: it is the decrease in the size of a normally developed organ or tissue due to a decrease in the size and number of its cells, atrophy may be:
1 – Physiological.
II- Disturbance leading to excessive growth, e.g. hypertrophy, hyperplasia.
1- Hypertrophy: means an abnormal increase in the
size of some tissue or organ due to increase in the size
of its cells in order to increase its functional capacity
to meet increased demands. Hypertrophy may be:
a- Physiological e.g. muscles of athletes, pregnant uterus.
b- Pathological: e.g. walls of left ventricle undergo hypertrophy in cases of hypertension of aortic stenosis or incompetence.
2- Hyperplasia: it is increase in the size of an organ or
tissues due to increase in the number of its cells.
– The pattern of hyperplastic tissue is essentially like that of site of origin.
- Hyperplasia persists only as long as the stimulus is acting i.e. it is a reversible process.
- Prolonged hyperplasia of breast, endometrium and thyroid may pass to neoplasia.
Ill- Disorders of cellular differentiation e.g. metaplasia dysplasia, anaplasia.
1- Metaplasia: means the change of a differentiated cell to another differentiated cell of the same category.
Types of metaplasia:
i. Epithelial metaplasia:
a) Squamous metaplsia may result from:
1- Chronic inflammation: transitional or
columnar epithelium in bilharzial cystitis,
chronic bronchitis, or chronic cholecystitis
may change into more resistant stratified
2- Vitamin A deficiency.
b) Glandular metaplasia: This is much less common.
An example is cystitis glandularis.
ii. Connective tissue metaplasia:
• Fibroblasts change into osteoblasts which build up osseous tissue “ossification” this occurs in:
- Old scars.
c) Calcified tuberculous lesions.
• Cartilage in larynx and trachea change into osteoblasts in old age.
iii- Tumor metaplasia:
This is particularly seen in carcinoma of endometrium in which the malignant tumor starts as adenocarcnoma but some of its malignant cells may change into squamous cells, leading to adenoacanthoma or adenosquamous carainoma.
2- Dysplasia: means the appearance of abnormal
undifferentiated hyperplastic cells within the normal
- It develops more commonly in the stratified squamous epithelium in the cervix uteri, larynx.
- Dysplastic cells are irregularly arranged, enlarged have dark nuclei which are of variable sizes.
- Dysplasia may be reversible if the cause disappears or it may proceed to pre-invasive carcinoma or carcinoma in situ.
3- Anaplasia: it is a term which is applied when a relatively
differentiated cell is changed to a less differentiated cell. It
is applied only to tumor cells.