Mechanisms of Atrophy - diagram

Atrophy is defined as a reduction in the mass of an organ after normal growth has been attained. The organ can be reduced in mass because of a decrease in the size of the cells (quantitative atrophy) or because of a decrease in the number of cells (numeri

Chicken: muscle: atrophy (generalized)

This chicken is severely emaciated. Note the reduction in the muscle mass throughout the body, especially in the pectoral muscles. Also note the prominence of the sternum or keel bone. With generalized atrophy, you should think of nutritional causes (such

Canine: leg: nerogenic atrophy and compensatory hypertrophy

This slide demonstrates neurogenic atrophy of the right forelimb. Neurogenic atrophy is a form of disuse atrophy; because of damage to the nerve(s) innervating muscles, there is lack of electrical stimulation and a resulting decrease in the size of the mu

Rat: skeletal muscle: atrophy

In this slide, the myofibers in the center are of normal size. The myofibers to the extreme right are markedly atrophic as evidenced by the marked reduction in the width of the myofibers and the hypercellular appearance at this low magnification. The myof

Rat: skeletal muscle: atrophy

In this slide, we can see normal myofibers in cross-section at the upper-right. A few of the myofibers in this area are swollen and hypereosinophilic, suggesting degeneration. The myofibers in the lower half of the slide are markedly reduced in diameter a

Calf: skeletal muscle: fatty atrophy

In this slide, the normal myofibers are to the far left. The myofibers in the center are severely reduced in size, measuring at least 1/20 the diameter of the normal myofibers. In addition, the interstitium contains an increased amount of adipose tissue (

Bovine: liver: atrophy: starvation

This slide demonstrates the gross lesions of atrophy in the liver. Overall, the size of this liver is reduced. In addition, the capsule is grey and wrinkled (this is especially visible on the right side of the slide). A small piece of normal liver is show

Equine: liver: atrophy: malabsorption/chronic diarrhea

Here is another example of atrophy of the liver. Note the multifocal grey opacities of the capsule; these opacities are due to loss of parenchyma and collapse of the overlying fibrous connective tissue capsule. Note the grey tags on the capsule of the rig

Equine: liver: atrophy: malabsorption/chronic diarrhea

This is the same liver as shown in the previous slide. Note the grey opacities of the capsule near the top of this slide. The liver lobe has been lifted so you can see the fibrosis at the very edge.

Liver: atrophy

This photomicrograph of the liver looks hypercellular because of the decrease in the size of the cells and the size of the hepatic lobules. Even at this magnification, hepatic cords look thin, especially in the centrolobular zones (around the central vein

Liver: atrophy

This is a higher magnification of the previous slide to show the thinned hepatic cords.

Bovine: liver: atrophy and post necrotic scarring: fibrous atrophy

This liver is reduced in size and has multiple fibrous scars that are visible from the capsular surface. These depressed, coalescing white foci represent areas in which hepatocytes have been lost and replaced with fibrous connective tissue.

Canine: Brain: atrophy: compression: meningioma

This slide demonstrated atrophy of an organ due to compression by a slow-growing neoplastic mass. The neoplasm is a meningioma, a benign neoplasm of the meninges. Note how the neoplasm has replaced a large portion of the right cerebrum and is compressing

Canine: Brain: atrophy: compression: meningioma

This is a higher magnification of the previous slide showing the neoplasm and a portion of the adjacent, compressed neuropil to the left. The slowly enlarging mass is compressing smaller blood vessels, resulting in ischemic necrosis of the adjacent parenc

Canine: kidney: atrophy: fibrous atrophy

Disturbances of growth are easier to diagnose in paired organs if only one organ in the pair is affected. Here we have the two kidneys from a dog. The right kidney (located to the left in this slide) is normal and measures approximately 7 cm in length. Th

Canine: kidney: atrophy: fibrous atrophy

This slide shows the cut surface of the kidneys seen in the previous slide. Note the ratio of the cortex to the medulla in both kidneys; both the amount of cortex and medulla are reduced in the atrophic kidney, but the cortex is reduced disproportionally

Equine: cerebellum: normal

One cerebellar folia is located in the center of this photomicrograph and the normal layered pattern can be readily seen. The leptomeninges, which is artefactually separated in this section, is the thin fibrovascular layer on the surface. The molecular la

Equine: cerebellum: abiotrophy

Here at about the same magnification as in the previous slide, you can see two small cerebellar folia with poorly defined layers. A thin, outer, eosinophilic layer represents the molecular layer and the few scattered basophilic nuclei represent the remnan

Equine: cerebellum: abiotrophy

Normal and affected folia are in this field. In this slide, the normal layered pattern of a cerebellar folia is seen at the left. At the upper-right are 4 extremely small folia with a few cells of the granular cell layer.

Porcine: Cerebellum: hypoplasia: normal and hypoplastic: hog cholera virus

Compare the size of the two cerebellums shown here. The one on the right is smaller than the one on the left (normal). One cause of this lesion in pigs is an in utero infection with hog cholera virus.

Porcine: cerebellum: Hypoplasia/Aplasia: Hog cholera virus

In this case, severe destruction of the cerebellum resulted from an in utero infection with hog cholera virus. Since only a small portion of the cerebellar peduncle can be found, this lesion would be most appropriately described as cerebellar aplasia.

Bovine: cerebellum: Hypoplasia/Aplasia: Bovine Viral Diarrhea virus

This slide shows a case of cerebellar aplasia in a calf due to an in utero infection with Bovine Viral Diarrhea (BVD) virus. Note the loose, vascularized tissue (choroid plexus) at the site where the cerebellum should be. This virus, as well as hog choler

Bovine: enamel: hypoplasia: chronic fluoride toxicosis

The blackened areas on these teeth represent areas of enamel hypoplasia due to the effects of excess fluoride. Excessive fluoride affects the odontoblasts and ameloblasts of the developing permanent teeth, resulting in a decrease in the quantity and quali

Bovine: colon: aplasia: atresia coli

This slide shows the colon of a calf with atresia coli. To the left, is the thin, empty segment of the rectum and distal colon. It is completely separated from the dilated, proximal sections of colon, located to the right. In this case, the two discontinu

Mechanisms of Hypertrophy - diagram

This diagram indicates that gross enlargement of an organ can occur by an increase in cell size (hypertrophy) or an increase in cell number (hyperplasia). Often time, gross hypertrophy is due to both cellular hypertrophy and cellular hyperplasia. In organ

Canine: right heart: hypertrophy & dilation: secondary to heartworms

Note the enlargement of the right ventricle due to cellular hypertrophy. This animal had heartworms (Dirofilaria immitus) in the pulmonary artery, resulting in increased vascular resistance and right ventricular dilatation and hypertrophy.

Canine: right heart: hypertrophy & dilation: secondary to pulmonic stenosis

This heart is from an dog with pulmonic stenosis. Note that the right ventricle (on the left) is about the same thickness as the left ventricle (on the right). Normally, the left ventricle is three times as thick as the right ventricle.

Feline: left heart: hypertrophy: cardiomyopathy

This is the opened left ventricle of a cat with hypertrophic cardiomyopathy. The left ventricular wall is about twice as thick as normal. In this disease, the ventricle can sometimes get so thick that the chamber is reduced to a small slit, resulting in a

Equine: normal skin

This is a section of normal skin from a horse. Note the thickness of the keratin layer (which is artefactually separated from the epidermis) and the 5-6 layers of cells in the epidermis.

Equine: skin: hyperplasia: acanthosis and parakeratosis: Zn deficiency

In this section of equine skin, note the marked thickness of the epidermis (epidermal hyperplasia). The increase in thickness is primarily due to proliferation of the stratum spinosum (acanthosis). Also note the mild increase in thickness of the keratin l

Equine: stomach: hyperplasia

This is the opened stomach from a horse, with the glandular portion to the right and the squamous portion to the left. The white, glistening area in the squamous portion of the stomach represents the normal mucosa. The rough, raised, yellow areas represen

Equine: stomach: hyperplasia

This is a higher magnification of the previous slide at the margo plicatus (margin of the glandular and squamous portions of the stomach). The yellow, raised, dull areas represent epithelial hyperplasia and the irregular, depressed, red foci at the right

Canine: gingiva: hyperplasia

In this slide, we see severe gingival hyperplasia, a proliferative response seen in chronic gingivitis or periodontal disease. Proliferation occurs in both the epithelium and underlying stroma. Note the dull, rough, gingival tissue that is so thick in som

Ovine: thyroid: hyperplasia: goiter

The red-brown, symmetrical, cervical mass represents enlarged thyroid glands. Thyroid gland enlargement is also known as goiter and is likely due to both hyperplasia and hypertrophy.

Ovine: thyroid: hyperplasia and normal: goiter

In this slide, we have normal thyroid glands on the right and hyperplastic thyroid glands on the left. Name 4 causes of thyroid gland hyperplasia.

Ovine: normal thyroid

This is a photomicrograph of a normal thyroid. Note the single layer of cuboidal epithelium lining the follicles and the proteinaceous colloid in lumina.

Ovine: thyroid: hyperplasia: goiter

In this section from a hyperplastic thyroid gland, note the increase in the number of follicles and the reduction in the luminal contents.

Ovine: thyroid: hyperplasia: goiter

This is a higher magnification of the previous slide. Note that follicular epithelial cells are columnar and vacuolated. Hypertrophy and hyperplasia are both evident in this slide. Four causes of thyroid gland hyperplasia are 1) decrease iodine, 2) increa

Feline: bone marrow: hyperplasia: myeloid hyperplasia

For an adult animal, the bone marrow on the left is normal; the yellow contents in the medullary cavity represents adipose tissue. Hemapoiesis in adult long bones takes place in the diaphysis (not in view here) and in a thin zone adjacent to the endosteum

Feline: spleen: follicular hyperplasia

In follicular hyperplasia of the spleen, the splenic follicles (white pulp) proliferate, usually in response to some antigenic stimulus. These hyperplastic follicles are seen as the numerous, 2-3 mm, white foci that are raised on the cut surface.

Canine: spleen: nodular hyperplasia

Nodular hyperplasia is another form of hyperplasia seen in the spleen. In this slide, note the larger, variably-sized, round, red nodules that are raised on the capsular surface. These represents areas of lymphocyte proliferation. Splenic nodular hyperpla

Canine: jaw: hyperplasia: parathyroid; rubber jaw; renal secondary hyperparathyroidism

The next series of slides are from a dog with renal secondary hyperparathyroidism. With renal disease, there is an increase in serum phosphorus that inhibits the production of active Vitamin D3 in the kidney. In response, continual production of parathyro

Canine: jaw: hyperplasia: parathyroid; rubber jaw; renal secondary hyperparathyroidism

Because of the calcium resorption from bone, the bones are extremely soft and fragile. In the case shown here, the mandible can be easily twisted.

Canine: jaw: hyperplasia: parathyroid; rubber jaw; renal secondary hyperparathyroidism

One of the thyroid glands is located in the center of this slide. Visible on the surface are two enlarged, parathyroid glands. Normally the parathyroid glands should measure 2-3 mm in diameter, but these glands are 3 times larger than normal (unfortunatel

Canine: jaw: hyperplasia: parathyroid; rubber jaw; renal secondary hyperparathyroidism

In this photomicrograph, the enlarged parathyroid gland is compressing the adjacent thyroid gland (top). The parathyroid gland is at least 5 times normal size and it is enlarged because of both hyperplasia and hypertrophy. What is the difference between h

Canine: jaw: hyperplasia: parathyroid; rubber jaw; renal secondary hyperparathyroidism

In this slide, the hypertrophic and hyperplastic parathyroid gland is located to the right. Thyroid gland, with colloid filled acini, is located to the left. Answers to the questions posed in the previous caption: Hyperparathyroidism refers to the clinica

Monkey: hyperplasia: nutritional secondary hyperparathyroidism

Here is another case of secondary hyperparathyroidism. In this case, the cause is nutritional. New World monkeys require a dietary source of Vitamin D3, since they cannot manufacture their own. These animals were deficient in Vitamin D3, resulting in hypo

Monkey: hyperplasia: nutritional secondary hyperparathyroidism

This transverse section through the maxilla shows the marked thickening of the bone.

Monkey: hyperplasia: nutritional secondary hyperparathyroidism

This trichrome-stained section reveals that the thickening of the maxilla is due to proliferation of fibrous connective tissue, which stains green. The red stain indicates mineralized tissue; note that the red is limited to the teeth and the remaining thi

Monkey: hyperplasia: nutritional secondary hyperparathyroidism

This is a higher magnification of the affected bone shown in the previous slide. A few trabeculae of bone, with osteocytes in lacunae, are visible. The space between the trabecule is filled with fibrous connective tissue composed of numerous spindle-shape

Monkey: hyperplasia: nutritional secondary hyperparathyroidism

Here is a long bone from a monkey with Vitamin D3 deficiency. In a normal long bone, you would expect to fine an outer cortex, made of cortical or woven bone, and an inner medullary cavity, filled with trabecular bone. In this case, no cortical bone is pr

Canine: hyperplasia: HPO

The next series of slides shows hyperplastic changes in bone. The disease condition highlighted is hypertrophic pulmonary osteoarthropathy (HPO) or hypertrophic osteopathy (HO). This is a rare condition is which there is hyperplasia of periosteal bone, pa

Canine: hyperplasia: HPO

In this gross specimen, you can see the rough proliferation of periosteal bone. In the cross-section, you can identify the boundaries of the normal cortex and see the expansion of the bone due to new periosteal bone formation. This is the same type of rea

Canine: hyperplasia: HPO

This slide represents a cross-section through the metacarpals bones. The boundaries of the original cortex can be identified. The boundaries of new bone formation indicate an increase in the thickness of these bones that is 2-3 times normal.

Canine: hyperplasia: HPO

This slide represents the histologic correlate to the previous slide. With this special stain, mineralized bone stains red. The original cortex of the bones and the radiating trabeculae of new periosteal bone can be identified.

Canine: hyperplasia: HPO

This is a higher magnification of one of the bones shown in the previous slide. The original cortex is at the right and shows a slight loss in cancellous bone. The new periosteal bone forms trabeculae that are arranged perpendicularly to the cortex.

Feline: Hypertrophy & hyperplasia: arterial medial hypertrophy

Note this extremely thick arteriole in the lung of a cat. The enlargement is due to both cellular hypertrophy and hyperplasia. This is a change that is seen commonly in cats and is attributed to infections with Aelurostrongylus abstrusus (a nematode that

Canine: liver: nodular hyperplasia

This slide shows numerous hyperplastic nodules in a cirrhotic liver. Cirrhosis is end-stage liver disease characterized by hepatic fibrosis and hepatic regeneration, usually in the form of nodular hyperplasia. The numerous, raised, hyperplastic nodules ar

Canine: liver: nodular hyperplasia with fatty change

Here is another example of nodular hyperplasia in a liver without cirrhotic change. The slightly raised, pale yellow foci represent the areas of nodular hyperplasia.

Canine: liver: nodular hyperplasia with fatty change

This is a higher magnification to show the pale yellow foci of nodular hyperplasia. The pale yellow color is due to fatty change within the hepatocytes of the hyperplastic nodule.

Rabbit: eye: squamous metaplasia: xerophthalmia: vitamin A deficiency

Vitamin A deficiency results in squamous metaplasia in a number of sites. The large, white opacity of the cornea represents squamous metaplasia in this experimental case of vitamin A deficiency. Squamous metaplasia may also be present in the lacrimal glan

Rabbit: cornea: squamous metaplasia: Vitamine A deficiency

This is a photomicrograph of the cornea taken at the fornix. At this magnification, you can see keratin and cellular debris in the conjunctival sac and an inflammatory cell infiltrate in the superficial cornea.

Rabbit: cornea: squamous metaplasia: Vitamine A deficiency

This is a higher magnification of the previous slide. The corneal epithelium is normally stratified squamous, but here we can see keratinization of the superficial layers (most evident at the left). Keratitis (inflammation of the cornea) and debris within

Rabbit: cornea: squamous metaplasia: Vitamine A deficiency

This slide demonstrates squamous metaplasia of the pelvis of the kidney. The renal pelvis is normally lined by transitional epithelium, but here we see a thick layer of keratined, stratified squamous epithelium.

Rabbit: cornea: squamous metaplasia: Vitamine A deficiency

This is a higher magnification of the previous slide showing the keratinized stratified squamous epithelium at the renal pelvis.

Canine: Osseous metaplasia: dural ossification

This slide demonstrated fibrous connective tissue that has transformed into bone. The red-brown plaques seen in the dura mater of the spinal cord represent areas of bone formation. This condition is seen in older animals and the cause is unknown. No clini

Canine: Osseous metaplasia: dural ossification

This is a higher magnification of the previous slide. The red-brown plaques represent areas of bone formation. Many of these contain hematopoietic bone marrow, thus giving the lesion its reddish color.

Equine: adrenal gland: nodular hyperplasia

Note the yellow nodules that are raised above the capsular surface of this adrenal gland. These are foci of nodular hyperplasia. These are often seen in older animals and may be functional.

Feline: adrenal gland: nodular hyperplasia

Comparable lesion in a cat. Cross-section of the adrenal gland. In the middle two cross-sections, you can see multifocal irregularities in the zona glomerulosa, the outer, light yellow-tan layer of the adrenal gland. The cross-section on the left has two

Bovine: Skin: hyperplasia: dermatomycosis

Lesion around the eye of a cow. Note the spectacled appearance of this cow. The white ring around the right eye represents thick, hyperkeratotic skin with alopecia. This is a classic lesion for ringworm or dermatomycosis. Proliferative and alopecic lesion

Procine: skin: alopecia & hyperlasia: dematomycosis

Comparable lesion in the skin of a pig. This lesion from the skin of a pig demonstrates that the disease is aptly named by the layman's term of ringworm. The red ring is due to active infection and inflammation at the advancing edge of the lesion. The bes

Bovine: heart/epicardial fat: serous atrophy of fat

The epicardial fat has a wet, shiny, gelatinous appearance. This change indicated resorption of lipids from adipose tissue stores. Look for causes of wasting, such as starvation, intestinal inflammation, poor quality feed, cancer, etc

Bovine: heart/epicardial fat: serous atrophy of fat

The amount of epicardial fat is greatly reduced and the remaining fat is wet, shiny, gelatinous and soft. The same change can be seen in mesenteric and perirenal fat.

Bovine: marrow: serous atrophy of fat

With serous atrophy of fat, bone marrow fat appears translucent and gelatinous. The red-tinge to the marrow fat is due to staining with hemoglobin (hemoglobin imbibition).

Equine: epicardial fat: serous atrophy of fat

Note the loss of adipocytes and replacement with homogeneous to granular eosinophilic material in the stroma; this material represents edema fluid.