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New page: {{review}} {{toplink |linkpage =General Pathology |linktext =General Pathology |maplink = General Pathology (Content Map) |pagetype =Pathology }} <br> ==Atrophy== * Atrophy is a decrease ...
{{review}}
{{toplink
|linkpage =General Pathology
|linktext =General Pathology
|maplink = General Pathology (Content Map)
|pagetype =Pathology
}}
<br>
==Atrophy==
* Atrophy is a decrease in the size of the cells and organ, occurring after the organ has reached normal size.
===Appearance===
* Atrophic tissues and organs appear smaller and perhaps paler than usual.
* Microscopy of atrophic tissue shows:
** Cells of a smaller size.
** Inactive appearance.
** A relative increase in the supportive connective tissue.
===Causes===
* Starvation
* Malabsorption
* Compression
** E.g by a nearby lesion.
* Immobilisation
** Immobilisation of a limb results in atrophy of the muscles.
* Denervation
* Lack of trophic hormones
* Chronic inflammation
** May be idiopathic.
===Examples===
====Serous Atrophy of Adipose Tissue====
* Also known as gelatinous atrophy of adipose tissue.
* The fat becomes transparent, watery and severely depleted.
* Occurs as a result of severe debilitation and weight loss.
====Brown Atrophy====
* A senile change in muscles where they appear brownish rather than reddish in colour.
* Due to the intracytoplasmic accumulation of [[General Pathology - Pigmentation and Calcification#Lipofuscin|lipofuscin]] within the muscle fibres.
** The "wear and tear" pigment.
==Hypertrophy==
* Hypertrophy is an increase in the size of an organ due to an increase in size of the individual cells.
** The organ also gains in weight.
===Types===
====Functional Hypertrophy====
* Occurs in response to:
** An increased physiological need.
*** E. g. muscles of the heart and limbs in training.
** An increased demand because of organ dysfunction.
*** E.g in cardiac hypertrophy due to a progressively failing heart.
====Compensatory Hypertrophy====
* Occurs when one of a paired organ is damaged or lost.
** E.g. the kidney.
====Obstructional Hypertrophy====
* Hollow organs may become thickened around an obstruction.
** E. g. intestine, bladder, [[Gall Bladder - Anatomy & Physiology|gall bladder]].
====Hormonal Mediated Hypertrophy====
* Anabolic steroids produce hypertrophy of muscle.
* Thyroid hormones have a general hypertrophic effect on tissues.
** Increase protein synthesis within them.
** The heart can become quite hypertrophied in thyroid excess.
*** Commonly seen in older cats which often develop hyperthyroidism.
==Hypoplasia==
* Hypoplasia is a reduction in the size of cells and tissues,.
* Due to a failure to grow to normal size.
* Ranges from mild hypoplasia to almost complete absence.
** Almost complete absence is also called vestigial or rudimentary.
* Aplasia and agensis refer to complete absence of tissue.
** Generally refer to the gross appearance rather than the microscopic appearance.
*** Some rudimentary tissue can be seen if searched for carefully.
==Hyperplasia==
* Hyperplasia is an increase in the size of an organ due to an increase in the numbers of cells present within it.
* Hypertrophy and hyperplasia may occur concurrently.
* The hyperplastic response stops when the inciting agent ceases.
* Hyperplastic tissue is more prone to injury by chemicals, and also may be more prone to undergo neoplastic change in some cases.
===Causes===
[[Image:benign prostatic hyperplasia.jpg|thumb|right|150px|Benign prostatic hyperplasia (Courtesy of BioMed Archive)]]
* Hormonal stimulation.
** Parathyroid hyperplasia in chronic renal failure.
** Prostatic hyperplasia in older dogs.
* Hyperplasia may also occur as a regenerative response to
** Irritation
** Cell loss
** Injury
===Gross Appearance===
* Hyperplastic nodules can be seen in a variety of organs in older dogs and cats.
** Particularly the thyroid in cats, and the spleen and [[Liver - Anatomy & Physiology|liver]] of dogs.
===Histological Appearance===
* Hyperplasia is characterised by an increase in the numbers of cells.
* Mitotic activity is not always seen.
* There is some increase in cellular basophilia.
* The cells are well differentiated and tissue structure is normal.
==Metaplasia==
* Metaplasia is a transformation of one type of tissue into another.
* Occurs solely in:
** '''Connective tissue'''
*** The metaplastic change id to cartilage and bone in damaged tissue.
*** Caesarean scars in the pig are especially prone to osseous metaplasia.
** '''Epithelium'''
*** Squamous metaplasia of cuboidal or columnar epithelium is quite common.
**** Seen in the prostate of dogs under the influence of oestrogens.
***** Oestrogens are present in Sertoli cell tumours and in Vit. A deficiency.
**** The most striking example is the squamous metaplasia of the oesophageal glands in the chicken.
* Mixed tumours of the mammary gland of the dog are so called because there is proliferation of both the glandular element and the surrounding myoepithelium.
** The myoepithelium can transform into cartilage and bone.
*** Some regard this as a metaplastic change.
*** The bone formed may even show marrow formation within the spaces between the bony trabeculae.
==Dysplasia==
* Dysplasia is abnormal growth within a tissue.
* The normal arrangement and pattern of the tissue may be lost.
* The most common example is the renal dysplasia in some breeds of dogs.
** Causes fibrous tracts.
** Because of the reduction in functional tissue, gives a predisposition to renal failure early in life in the more severely affected cases.
==Anaplasia==
* Anaplasia is a marked and irreversible loss of cellular differentiation with return to a more primitive state.
* Afeature of highly malignant tumours.
* There is no pattern, just a diffuse sheet of cells.
* Both cells and nuclei are of differing sizes.
* There are prominent nucleoli in some nuclei.
==[[General Pathology - Neoplasia|Neoplasia]]==
*[[General Pathology - Neoplasia#Neoplasia|Introduction]]
*[[General Pathology - Neoplasia#Classification|Classification]]
*[[General Pathology - Neoplasia#Nomenclature|Nomenclature]]
*[[General Pathology - Neoplasia#Causes of Neoplasia|Causes of neoplasia]]
*[[General Pathology - Neoplasia#Tumour Assessment|Tumour assessment]]
*[[General Pathology - Neoplasia#Phases of Tumour Development|Phases of tumour development]]
*[[General Pathology - Neoplasia#Growth of Tumours|Growth of tumours]]
*[[General Pathology - Neoplasia#Dissemination of Malignant Neoplasia|Dissemination of malignant neoplasia]]
*[[General Pathology - Neoplasia#Tumour Grading and Staging|Tumour grading and staging]]
*[[General Pathology - Neoplasia#Pathological Effects|Pathological effects]]
*[[General Pathology - Neoplasia#Tumour Markers|Tumour markers]]
*[[General Pathology - Neoplasia#Tumour Immunity|Tumour immunity]]
*[[General Pathology - Neoplasia#Examples of Tumour Types|Examples of tumour types]]
{{toplink
|linkpage =General Pathology
|linktext =General Pathology
|maplink = General Pathology (Content Map)
|pagetype =Pathology
}}
<br>
==Atrophy==
* Atrophy is a decrease in the size of the cells and organ, occurring after the organ has reached normal size.
===Appearance===
* Atrophic tissues and organs appear smaller and perhaps paler than usual.
* Microscopy of atrophic tissue shows:
** Cells of a smaller size.
** Inactive appearance.
** A relative increase in the supportive connective tissue.
===Causes===
* Starvation
* Malabsorption
* Compression
** E.g by a nearby lesion.
* Immobilisation
** Immobilisation of a limb results in atrophy of the muscles.
* Denervation
* Lack of trophic hormones
* Chronic inflammation
** May be idiopathic.
===Examples===
====Serous Atrophy of Adipose Tissue====
* Also known as gelatinous atrophy of adipose tissue.
* The fat becomes transparent, watery and severely depleted.
* Occurs as a result of severe debilitation and weight loss.
====Brown Atrophy====
* A senile change in muscles where they appear brownish rather than reddish in colour.
* Due to the intracytoplasmic accumulation of [[General Pathology - Pigmentation and Calcification#Lipofuscin|lipofuscin]] within the muscle fibres.
** The "wear and tear" pigment.
==Hypertrophy==
* Hypertrophy is an increase in the size of an organ due to an increase in size of the individual cells.
** The organ also gains in weight.
===Types===
====Functional Hypertrophy====
* Occurs in response to:
** An increased physiological need.
*** E. g. muscles of the heart and limbs in training.
** An increased demand because of organ dysfunction.
*** E.g in cardiac hypertrophy due to a progressively failing heart.
====Compensatory Hypertrophy====
* Occurs when one of a paired organ is damaged or lost.
** E.g. the kidney.
====Obstructional Hypertrophy====
* Hollow organs may become thickened around an obstruction.
** E. g. intestine, bladder, [[Gall Bladder - Anatomy & Physiology|gall bladder]].
====Hormonal Mediated Hypertrophy====
* Anabolic steroids produce hypertrophy of muscle.
* Thyroid hormones have a general hypertrophic effect on tissues.
** Increase protein synthesis within them.
** The heart can become quite hypertrophied in thyroid excess.
*** Commonly seen in older cats which often develop hyperthyroidism.
==Hypoplasia==
* Hypoplasia is a reduction in the size of cells and tissues,.
* Due to a failure to grow to normal size.
* Ranges from mild hypoplasia to almost complete absence.
** Almost complete absence is also called vestigial or rudimentary.
* Aplasia and agensis refer to complete absence of tissue.
** Generally refer to the gross appearance rather than the microscopic appearance.
*** Some rudimentary tissue can be seen if searched for carefully.
==Hyperplasia==
* Hyperplasia is an increase in the size of an organ due to an increase in the numbers of cells present within it.
* Hypertrophy and hyperplasia may occur concurrently.
* The hyperplastic response stops when the inciting agent ceases.
* Hyperplastic tissue is more prone to injury by chemicals, and also may be more prone to undergo neoplastic change in some cases.
===Causes===
[[Image:benign prostatic hyperplasia.jpg|thumb|right|150px|Benign prostatic hyperplasia (Courtesy of BioMed Archive)]]
* Hormonal stimulation.
** Parathyroid hyperplasia in chronic renal failure.
** Prostatic hyperplasia in older dogs.
* Hyperplasia may also occur as a regenerative response to
** Irritation
** Cell loss
** Injury
===Gross Appearance===
* Hyperplastic nodules can be seen in a variety of organs in older dogs and cats.
** Particularly the thyroid in cats, and the spleen and [[Liver - Anatomy & Physiology|liver]] of dogs.
===Histological Appearance===
* Hyperplasia is characterised by an increase in the numbers of cells.
* Mitotic activity is not always seen.
* There is some increase in cellular basophilia.
* The cells are well differentiated and tissue structure is normal.
==Metaplasia==
* Metaplasia is a transformation of one type of tissue into another.
* Occurs solely in:
** '''Connective tissue'''
*** The metaplastic change id to cartilage and bone in damaged tissue.
*** Caesarean scars in the pig are especially prone to osseous metaplasia.
** '''Epithelium'''
*** Squamous metaplasia of cuboidal or columnar epithelium is quite common.
**** Seen in the prostate of dogs under the influence of oestrogens.
***** Oestrogens are present in Sertoli cell tumours and in Vit. A deficiency.
**** The most striking example is the squamous metaplasia of the oesophageal glands in the chicken.
* Mixed tumours of the mammary gland of the dog are so called because there is proliferation of both the glandular element and the surrounding myoepithelium.
** The myoepithelium can transform into cartilage and bone.
*** Some regard this as a metaplastic change.
*** The bone formed may even show marrow formation within the spaces between the bony trabeculae.
==Dysplasia==
* Dysplasia is abnormal growth within a tissue.
* The normal arrangement and pattern of the tissue may be lost.
* The most common example is the renal dysplasia in some breeds of dogs.
** Causes fibrous tracts.
** Because of the reduction in functional tissue, gives a predisposition to renal failure early in life in the more severely affected cases.
==Anaplasia==
* Anaplasia is a marked and irreversible loss of cellular differentiation with return to a more primitive state.
* Afeature of highly malignant tumours.
* There is no pattern, just a diffuse sheet of cells.
* Both cells and nuclei are of differing sizes.
* There are prominent nucleoli in some nuclei.
==[[General Pathology - Neoplasia|Neoplasia]]==
*[[General Pathology - Neoplasia#Neoplasia|Introduction]]
*[[General Pathology - Neoplasia#Classification|Classification]]
*[[General Pathology - Neoplasia#Nomenclature|Nomenclature]]
*[[General Pathology - Neoplasia#Causes of Neoplasia|Causes of neoplasia]]
*[[General Pathology - Neoplasia#Tumour Assessment|Tumour assessment]]
*[[General Pathology - Neoplasia#Phases of Tumour Development|Phases of tumour development]]
*[[General Pathology - Neoplasia#Growth of Tumours|Growth of tumours]]
*[[General Pathology - Neoplasia#Dissemination of Malignant Neoplasia|Dissemination of malignant neoplasia]]
*[[General Pathology - Neoplasia#Tumour Grading and Staging|Tumour grading and staging]]
*[[General Pathology - Neoplasia#Pathological Effects|Pathological effects]]
*[[General Pathology - Neoplasia#Tumour Markers|Tumour markers]]
*[[General Pathology - Neoplasia#Tumour Immunity|Tumour immunity]]
*[[General Pathology - Neoplasia#Examples of Tumour Types|Examples of tumour types]]