29.- EMBRYOLOGY

29.- EMBRYOLOGY

Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is a science which is about the development of an embryo from the fertilization of the ovum to the fetus stage.

PREGNANCY

Pregnancy is the fertilization and development of one or more offspring, known as an embryo

or fetus, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Childbirth usually occurs about 38 weeks after conception; in women who have a menstrual cycle length of four weeks, this is approximately 40 weeks from the start of the last normal menstrual period (LNMP). Human pregnancy is the most studied of all mammalian pregnancies. Conception can be achieved through sexual intercourse or assisted reproductive technology.

An embryo is the developing offspring during the first 8 weeks following conception, and subsequently the term fetus is used henceforth until birth. 40% of pregnancies in the United States and United Kingdom are unplanned, and between a quarter and half of those unplanned pregnancies were unwanted pregnancies.

In many societies’ medical or legal definitions, human pregnancy is somewhat arbitrarily divided into three trimester periods, as a means to simplify reference to the different stages of prenatal development. The first trimester carries the highest risk of miscarriage (natural death of embryo or fetus). During the second trimester, the development of the fetus can be more easily monitored and diagnosed. The beginning of the third trimester often approximates the point of viability, or the ability of the fetus to survive, with or without medical help, outside of the uterus.

DRUG

A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are

different meanings in drug control law, government regulations, medicine, and colloquial usage.

In pharmacology, a drug is "a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being." Drugs may be prescribed for a limited duration, or on a regular basis for chronic disorders.

The molecules of drugs are complex, and most of them consist of many hydrogen and carbon atoms, a few oxygen atoms, and one or a few nitrogen atoms. Drugs may also have no nitrogen atoms in it and many may have chlorine atoms in it, such as chloral hydrate.

Recreational drugs are chemical substances that affect the central nervous system, such as opioids or hallucinogens.They may be used for perceived beneficial effects on perception, consciousness, personality, and behavior. Some drugs can cause addiction and/or habituation.
Drugs are usually distinguished from endogenous biochemicals by being introduced from

outside the organism. For example, insulin is a hormone that is synthesized in the body; it is called a hormone when it is synthesized by the pancreas inside the body, but if it is introduced into the body from outside, it is called a drug. Many natural substances, such as beers, wines, and psychoactive mushrooms, blur the line between food and recreational drugs, as when ingested they affect the functioning of both mind and body and some substances normally considered drugs such as DMT (Dimethyltryptamine) are actually produced by the human body in trace amounts.

CONGENITAL ABNORMALITY

A congenital anomaly (congenital abnormality, congenital malformation, birth defect) is a condition which is present at the time of birth which varies from the standard presentation. It is a type of congenital disorder which is primarily structural in nature

AGING AND DEATH

Aging (American English, occasionally British English) or ageing (British English) is the accumulation of changes in a person over time. Aging in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of aging grow and expand over time, while others decline. Reaction time, for example, may slow with age, while knowledge of world events and wisdom may expand. Research shows that even late in life, potential exists for physical, mental, and social growth and development. Aging is an important part of all human societies reflecting the biological changes that occur, but also reflecting cultural and societal conventions. Roughly 100,000 people worldwide die each day of age-related causes.

DEATH

Death is the cessation or permanent termination of all biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, suicide, murder and accidents or trauma resulting in terminal injury. All known organisms inevitably experience death. Bodies of living organisms begin to decompose shortly after death. In human societies, the nature of death has for millennia been a concern of the world's religious traditions and of philosophical inquiry. This may include a belief in some kind of resurrection (associated with Abrahamic religions), reincarnation (associated with Dharmic religions), or that consciousness permanently ceases to exist, known as "oblivion" (often associated with atheism). Commemoration ceremonies after death may include various mourning or funeral practices. The physical remains of a person, commonly known as a corpse or body, are usually interred whole or cremated, though among the world's cultures there are a variety of other methods of mortuary disposal