Webster's New World Medical Dictionary

laceration
See 
cut.
lacrimal
Pertaining to tears. For example, the
lacrimal gland is a gland that secretes tears.
lacrimal gland
A small almond-shaped structure
that produces tears and is located just above the
upper, outer corner of the eye.
lacrimation
Shedding tears, or shedding more
tears than is normal (for example, as a result of eye
injury or irritation).
lactase
The enzyme that breaks down the milk
sugar lactose. Lactase is essential to digest lactose.
Without enough lactase, a person is lactose intoler-
ant. See also 
lactose intolerance.
lactase deficiency
See 
deficiency, lactase.
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lactation
The process of milk production.
Human milk is secreted by the mammary glands,
which are located within the fatty tissue of the
breast. The hormone oxytocin is produced in
response to the birth of a new baby, and it both stim-
ulates uterine contractions and begins the lactation
process. For the first few hours of nursing, a special
fluid called colostrum is delivered; colostrum is
especially high in nutrients, fats, and antibodies, to
protect the newborn from infection. Thereafter, the
amount of milk produced is controlled primarily by
the hormone prolactin, which is produced in
response to the length of time the infant nurses at
the breast. See also 
breastfeeding.
lactic acid
A simple sugar that is the byproduct of
glucose metabolism. Most lactic acid is produced by
the red blood cells and by muscle cells when oxygen
levels are low. When lactic acid accumulates rapidly
in the muscle cells during or just after exercise,
cramping can result. When lactic acid builds up
faster than it can be removed by the body, lactic aci-
dosis is the result. Lactic acidosis can occur with
intensive exercise or may be related to medical
conditions.
Lactobacillus
A bacterium normally found in the
mouth, intestinal tract, and vagina. Lactobacillus can
also live in fermenting products, such as yogurt.
Humans appear to have a symbiotic relationship with
this bacteria: some types have become an important