Lesson 3, Page 16 of 20

Achiria means congenital absence of one or both hands.

We learned that the prefix ec- (ex- before a vowel) means "out of" or "away from." We were introduced to this word element when we talked about the words appendectomy (to "cut out" the appendix) and hysterectomy (to "cut out" the uterus.)

An ectopic pregnancy is a pregnancy where the fertilized egg is implanted outside the uterine cavity, instead of on the inside of the uterus where it is normally implanted.

A related prefix is ecto- (ect- before a vowel) which means "outside of." The ectoderm is the outer layer of skin, for example.

Another related prefix is exo-, which means "outside, from the outside, or toward the outside."

An exotoxin [exo-, outside + tox, poison] is a toxin that is produced by a microorganism, such as a bacterium, and excreted into its surrounding medium. (As opposed to an endotoxin, which is a bacterial toxin confined within the body of the bacterium, released only when the bacterium is broken down.)

An exocrine gland [exo-, outside + crin, secrete] is a gland that secretes to the outside of an epithelial surface. (As opposed to endocrine glands which secrete into the bloodstream.) Sweat glands are examples of exocrine glands.

The prefix which means the opposite of exo- and ecto- is endo-, or ento- (end- or ent- before a vowel) which means "within." Some examples of words containing this prefix are:

endodontics [endo- + dont, tooth] - the branch of dentistry that deals with the inner portion of the tooth (where the root canals and nerves reside.)

endometritis [endo- + metr-, uterus + itis, inflammation] - inflammation of the mucous membrane lining the inner surface of the uterus.

An endocrine gland [endo- + crin, secrete] is a "ductless" gland that secretes its substance into the blood or lymph. (As opposed to exocrine glands, such as the sweat glands, that secrete to the outside.) The thyroid and adrenal glands are examples of endocrine glands.

The prefix hemi- means "half." A hemisphere for example is one half of a sphere or globe. Hemi- ofen refers to one side of the body as in the word hemiparalysis, which means paralysis on one side of the body.

What does hemialgia mean?

pain on one half of the body
pain on one side of the head
pain on both sides of the head
pain on both sides of the body