secretion

Examples of secretion in the following topics:

• Antibody Structure

  • After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood.
  • A small amount of IgA is also secreted into the serum in monomeric form.
  • Conversely, some IgM is secreted into bodily fluids of the mucosa.
  • Similarly to IgM, IgA molecules are secreted as polymeric structures linked with a J chain.
  • However, IgAs are secreted mostly as dimeric molecules, not pentamers.

• Neural Responses to Food

  • The salivary glands secrete more saliva in response to the stimulus presented by food in preparation for digestion.
  • The gastric and salivary secretion in the cephalic phase can also take place at the thought of food.
  • These responses stimulate secretions and powerful contractions.
  • The intestinal phase begins when chyme enters the small intestine, triggering digestive secretions.
  • Seeing a plate of food triggers the secretion of saliva in the mouth and the production of hydrochloric acid in the stomach.

• Adrenal Glands

  • The adrenal glands consist of an outer adrenal cortex and an inner adrenal medulla, which secrete different hormones.
  • It signals the tubules in the kidney nephrons to reabsorb sodium while secreting or eliminating potassium.
  • Angiotensin stimulates aldosterone secretion.
  • Epinephrine is the primary adrenal medulla hormone, accounting for 75 to 80 percent of its secretions.
  • Secretion of these hormones is stimulated by acetylcholine release from pre-ganglionic sympathetic fibers innervating the adrenal medulla.

• The Endoplasmic Reticulum

  • These modified proteins will be incorporated into cellular membranes—the membrane of the ER or those of other organelles—or secreted from the cell (such as protein hormones, enzymes).
  • Since the RER is engaged in modifying proteins (such as enzymes, for example) that will be secreted from the cell, the RER is abundant in cells that secrete proteins.

• The Golgi Apparatus

  • In another example of form following function, cells that engage in a great deal of secretory activity (such as cells of the salivary glands that secrete digestive enzymes or cells of the immune system that secrete antibodies) have an abundance of Golgi.
  • Describe the structure of the Golgi apparatus and its role in protein modification and secretion

• Exocytosis

  • Some examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles.
  • Some examples of cells using exocytosis include: the secretion of proteins like enzymes, peptide hormones and antibodies from different cells, the flipping of the plasma membrane, the placement of integral membrane proteins(IMPs) or proteins that are attached biologically to the cell, and the recycling of plasma membrane bound receptors(molecules on the cell membrane that intercept signals).

• Immunological Memory

  • During the adaptive immune response to a pathogen that has not been encountered before, known as the primary immune response, plasma cells secreting antibodies and differentiated T cells increase, then plateau over time.
  • Memory B cells that differentiate into plasma cells output ten to hundred-fold greater antibody amounts than were secreted during the primary response .
  • In the primary response to infection, antibodies are secreted first from plasma cells.
  • Upon re-exposure to the same pathogen, memory cells differentiate into antibody-secreting plasma cells that output a greater amount of antibody for a longer period of time.

• Physical and Chemical Barriers

  • Both the innate and adaptive levels of the immune response involve secreted proteins, receptor-mediated signaling, and intricate cell-to-cell communication.
  • These include tears in the eyes; mucous membranes that provide partial protection despite having to allow absorption and secretion; mucus secretions that trap and rinse away pathogens; and cilia (singular cilium) in the nasal passages and respiratory tract that push the mucus with the pathogens out of the body .
  • Furthermore, tears and mucus secretions contain microbicidal factors that prevent many infections from entering via these routes.

• Pineal Gland and Gonads

  • The pineal gland is responsible for melatonin production, while the gonads secrete hormones relating to sexual characteristic development.
  • The main hormone produced and secreted by the pineal gland is melatonin.
  • Progesterone is a female hormone secreted by the corpus luteum after ovulation during the second half of the menstrual cycle.

• Kidney Function and Physiology

  • Urine is a byproduct of the osmoregulatory function of kidneys, which filter blood, reabsorb water and nutrients, and secrete wastes.
  • The formation of urine occurs through three steps: glomerular filtration, tubular reabsorption, and tubular secretion.
  • Additional solutes and wastes are secreted into the kidney tubules during tubular secretion, which is the opposite process to tubular reabsorption.