epithelia III B Flashcards
The secretions from both exocrine and endocrine glands are generally regulated by:
the autonomic nervous system (i.e. by direct neuronal stimulation), by hormones from blood, or by both.
Exocrine glands often secrete
continuously at a low rate but can be triggered to greatly increase the volumes of secretion by these mechanisms.
the sight or smell of food stimulates ______
serous secretions from salivary glands, and mucous and serous secretions from gastrointestinal glands.
Endocrine secretions tend to be tightly regulated by ______.
hormonal or neuronal stimulation
Epithelial tissues are targets _____.
(direct or indirect) of a large variety of diseases
Some examples of epithelial diseases are:
diabetes, various liver and kidney diseases, lung diseases (e.g. emphysema, cystic fibrosis), GI disease (e.g. gastric ulcers, inflammatory bowel diseases), skin diseases, hearing diseases, and ciliopathies
Examples in the gastrointestinal tract include:
ulcerative colitis, in which extensive ulceration and destruction of the absorptive epithelium occurs.
pemphigus is an
autoimmune disease in which antibodies are produced against components of desmosomes in skin, leading to extensive blistering.
the broad clinical importance of pemphigus is that:
their relatively high rate of turn-over requiring stem cell-driven renewal, and their exposure to external damage (UV light, pathogens, chemicals).
The most common cancers are _______
derived from epithelial tissue, probably because of damage exposure and their high stem-cell driven turnover rates.
Cancers of epithelial origin are called _____.
carcinomas
cancers derived from glandular epithelium are known as ______
adenocarcinomas.
Tumors usually first develop within an ______
epithelial sheet, but they can become invasive and spread (metastasize) to other parts of the body.
Often, carcinomas retain _______.
some properties of their tissue of origin.
It is now believed that carcinomas result from defects in _____
regulatory pathways that control epithelial stem cells or their progeny during tissue development and maintenance.
Targeted regulatory pathways include
- signaling systems that directly control development (e.g. Wnt, EGF or Notch signaling systems) 2. internal cell cycle control factors
- factors that control DNA damage repair
- apoptosis (programmed cell death)
the diagnosis and treatment of different carcinomas is aided by _____
histological appearance of the tumor and knowledge of epithelial biology.
Epithelia are also important to consider in_____.
wound repair
Injuries to skin epithelia that do not extensively damage the basal epithelial stem cells and basal lamina can often be repaired by _____, but if the basal skin layers and basal laminae are severely compromised, _____
intrinsic mechanisms
they are replaced by scar tissue
severe burns may require
skin grafts to replace a damaged basal lamina and restore a population of basal skin epithelial stem cells.
