The wonders of diarrhea

There are four mechanisms of diarrhea:
- malabsorption/ maldigestion

• example: result of selective deficiencies of brush border enzymes such as disaccharidases
• other possible causes: loss of enterocyte function, loss of absorptive surface area, non-intestinal causes
• osmotic diarrhea is typically a small intestine problem in small animals and can occur significantly in the colon of large animals.

- hypersecretion despite structurally intact muscosa

• electrolyte and fluid move into the intestinal lumen
• often associated with entertoxins of intraluminal pathogens, such as the heat stable toxin of E. coli and the virulence factors of Shigella and Salmonella

- exudative (due to direct damage to vessels or increased hydrostatic pressure)

• example 1: direct damage can be caused by Salmonellosis
• example 2: increased hydrostatic pressure can result from Johne's disease

- deranged intestinal motility

• hypomotility (abnormal proliferation of microflora) or hypermotility (reduced contact time)
• can be caused by tumors, foreign bodies, intussusception, strictures, acute inflammation

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Let's start learning about the nervous system

This packet starts off with some basic definitions. Below I've listed some that I thought might be hard to remember.

gemistocyte a hypertrophied astrocyte

gitter cell mononuclear phagocyte containing myelin debris

hydranencephaly large portion of cerebrum is missing and replaced by fluid-filled membranous sac. No identifiable cortex remains.

lissencephaly smooth-surfaced cerebrum (no gyral development). Usually cortex is thicker than normal (pachygyria).

myelitis inflammation of the spinal cord.

neuronophagia (process of neuronal phagocytosis) accumulation of mononuclear cells around/ at the site of a neuronal cell body undergoing dissolution/ has disappeared.

porencephaly cavities in the brain, usually the cerebrum.

satellitosis accumulation of glial cells (usually oligodendrocytes) around a neuronal cell body.

spina bifida failure of the vertebral arch to develop

spinal dysraphism abnormal spinal cord development with improper union between two contiguous structures.

syringiomyelia cavity in the spinal cord parenchyma, usually in the white matter.

Wallerian degeneration degenerative changes in an axon and its myelin distal to point of injury

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