Chapter 22 - Growth, development, and aging

Question 1

prenatal period vs postnatal period

Answer 1

The prenatal period begins at conception and ends at birth; the postnatal period begins at birth and continues until death.

Question 2

conception

Answer 2

also called fertilization
It is the moment the female ovum and the male sperm cells unite to form a zygote; it is the beginning of the life of an organism.

Question 3

embryology

Answer 3

the branch of biology and medicine concerned with the study of embryos and their development

Question 4

morula

Answer 4

an early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida

Question 5

zona pellucida

Answer 5

a glycoprotein layer surrounding the plasma membrane of mammalian oocytes

Question 6

blastomere

Answer 6

a type of cell produced by cleavage (cell division) of the zygote after fertilization and is an essential part of blastula formation

Question 7

blastulation vs. blastula

Answer 7

Blastulation is the stage in early animal embryonic development that produces the blastula. The blastula (from Greek βλαστός (blastos meaning sprout) is a hollow sphere of cells (blastomeres) surrounding an inner fluid-filled cavity (the blastocoel).

Embryonic development begins with a sperm fertilizing an egg cell to become a zygote, which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoel is formed does the early embryo become a blastula. The blastula grows to become a blastocyst.

Question 8

blastocyst

Answer 8

A blastula that has developed to the point where differentiation begins in its cells. The blastomeres in the blastula’s outer cell layer are replaced by a trophoblast.

As the blastocyst develops, it forms a structure with two cavities, the yolk sac and amniotic cavity.

Question 9

trophoblast

Answer 9

A thin layer of cells that helps a developing embryo attach to the wall of the uterus, protects the embryo, and forms a part of the placenta.

Question 10

pluripotent

Answer 10

(of an immature or stem cell) capable of giving rise to several different cell types

Question 11

laparoscope

Answer 11

a fiber-optic instrument inserted through the abdominal wall to view the organs in the abdomen or permit small-scale surgery

Question 12

yolk sac

Answer 12

In humans, a sac involved with the production of blood cells in the developing embryo.

The yolk sac is most important in animals, such as birds, that depend heavily on yolk as the sole source of nutrients for the developing embryo. In these animals, the yolk sac digests the yolk and provides the resulting nutrients to the embryo.

Because uterine fluids provide nutrients to the developing human embryo until the placenta develops, the function of the yolk sac is not a nutritive one. Instead, it has other functions—including production of blood cells.

Question 13

amniotic cavity

Answer 13

The amniotic cavity is the closed sac between the embryo and the amnion, containing the amniotic fluid.

Question 14

amnion

Answer 14

A membrane that closely covers the human and various other embryos when they are first formed. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the developing embryo.

Question 15

chorion

Answer 15

The outermost fetal membrane around the embryo in mammals, birds and reptiles. It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals).

Question 16

in vitro fertilization

Answer 16

The Latin term in vitro means, literally, “within a glass.” In the case of in vitro fertilization, it refers to the glass laboratory dish where an ovum and sperm are mixed and where fertilization occurs.

In the classic technique, the ovum is obtained from the woman by first inserting a fiber-optic viewing instrument called a laparoscope through a very small incision in her abdomen. After it is in the abdominal cavity, the device allows the physician to view the ovary, puncture it, and “suck up” an ovum from a mature follicle. Over the years refinements to this technique have been made, and less invasive procedures are currently being used.

After fertilization in a laboratory dish and about 2.5 days’ growth in a temperature-controlled environment, the developing zygote (which by then has reached the 8- or 16-cell stage) is placed by the physician into the mother’s uterus. If implantation is successful, growth will continue and the subsequent pregnancy will progress. In the most successful fertility clinics in the United States, a normal term birth will occur in about 30% of in vitro fertilization attempts.

Question 17

gastrulation

Answer 17

Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells) is reorganized into a multilayered structure known as the gastrula.

Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. dorsal-ventral, anterior-posterior), and internalized one or more cell types including the beginnings of the gastrointestinal tract.

Question 18

germ layer

Answer 18

a primary layer of cells that forms during embryonic development

Question 19

gastrula

Answer 19

An embryo at the stage following the blastula. It has a hollow cup-shaped structure having three layers of cells.

The gastrula is trilaminar (“three-layered”). These three germ layers are known as the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).

Question 20

Bilateria

Answer 20

also called bilaterians
They are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other.
Humans, cats, monkeys, frogs, and sharks are just some examples.

Question 21

choriocarcinoma

Answer 21

A malignant, fast-growing tumor that develops from trophoblastic cells (cells that help an embryo attach to the uterus and help form the placenta). Almost all choriocarcinomas form in the uterus after fertilization of an egg by a sperm.

Question 22

chorionic villi

singular: chorionic villus

Answer 22

Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood.

They are an essential element in pregnancy.

Branches of the umbilical arteries carry embryonic blood to the villi. After circulating through the capillaries of the villi, blood returns to the embryo through the umbilical vein.

Thus, villi are part of the border between maternal and fetal blood during pregnancy.

Question 23

lacuna

Answer 23

(1) a blank space or a missing part: GAP

(2) a small cavity, pit, or discontinuity in an anatomical structure

Question 24

villi

singular: villus

Answer 24

(biology) A small projection from a membrane, particularly those found in the mucous membranes of the intestines.
(botany) One of the fine soft hairs on fruits, flowers, and other parts of plants.

Question 25

parturition

Answer 25

the action or process of giving birth to offspring: childbirth

Question 26

gestation period

Answer 26

also simply called gestation

it is the entire length of pregnancy, from conception to birth, typically lasting 39 weeks (approximately 9 months)

the gestation period is typically divided into 3-month segments called trimesters

Question 27

three stages of prenatal development

Answer 27

The process of prenatal development (gestation) occurs in three main stages.

Germinal stage: Weeks 1-2. It starts as a zygote which transforms into a blastocyst. That blastocyst then attaches to the uterus (this is called implantation) and starts the next stage.
Embryonic stage: Weeks 3-8. Embryo forms the basic structures of the human body and becomes a fetus.
Fetal stage: Week 9 to birth. Fetus develops slowly into a fully formed baby.

Remember: zygote -> morula -> blastula -> blastocyst -> gastrula -> organogenesis

(zygote to blastocyst is germinal stage, gastrula then organogenesis occur in the embryonic stage, and organogenesis continues until birth)

Question 28

embryo vs fetus

Answer 28

When the baby-to-be is in the germinal or embryonic stage, it is called an embryo. When it moves into the fetal stage, it is called a fetus. It is mostly an arbitrary line.

However, an embryo is still in the process of laying the groundwork for what will later be the body organs. A fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional and some not yet situated in their final anatomical location.

Question 29

histogenesis

Answer 29

the differentiation of cells into specialized tissues and organs during growth

Question 30

organogenesis

Answer 30

the phase of embryonic development that starts at the end of gastrulation and continues until birth. During organogenesis, the three germ layers formed from gastrulation (the ectoderm, endoderm, and mesoderm) form the internal organs of the organism

Question 31

teratogen

Answer 31

an agent or factor which causes malformation of an embryo

Question 32

birth defect

Answer 32

a developmental problem present at birth

Question 33

mutagen

Answer 33

an agent, such as radiation or a chemical substance, which causes genetic mutation

Question 34

gerontology

Answer 34

the scientific study of old age, the process of aging, and the particular problems of old people

Question 35

geriatrics

Answer 35

the branch of medicine or social science dealing with the health and care of old people

Question 36

three stages of labor

Answer 36

Labor is the process that results in the birth of a baby. It has three stages:
1. Stage 1—period from onset of uterine contractions until dilation of the cervix is complete
2. Stage 2—period from the time of maximal cervical dilation until the baby exits through the vagina
3. Stage 3—process of expulsion of the placenta through the vagina
(dilation = opening up)

The process normally begins with the fetus taking a head-down position against the cervix. A breech birth is one in which the fetus fails to turn head downward and consequently the feet are born first. This condition usually requires the baby to be born by cesarean section. Often called simply a C-section, it is a surgical procedure in which the newborn is delivered through an incision in the abdomen and uterine wall. The procedure may be done when abnormal conditions of the mother or fetus (or both) make normal vaginal delivery hazardous or impossible.

Question 37

pre-labor

Answer 37

The early signs before labor starts. It is the body’s preparation for real labor.

As pregnancy draws to a close, the uterus becomes “irritable” and, ultimately, muscular contractions begin and cause the cervix to dilate or open, thus permitting the fetus to move from the uterus through the vagina, or “birth canal,” to the exterior. When contractions occur, the amniotic sac, or “bag of waters,” ruptures, and labor begins.

Question 38

Apgar score

Answer 38

A test given to newborns soon after birth. This test checks a baby’s heart rate, muscle tone, and other signs to see if extra medical care or emergency care is needed. The test is usually given twice: once at 1 minute after birth, and again at 5 minutes after birth.

There are five things the test checks for, represented by the backronym APGAR. Each thing is between 0 and 2 points, with 2 being the best. A healthy baby scores a 10 in total.

APGAR stands for Appearance, Pulse (heartrate), Grimace (crying), Activity (reflexes), and Respiration.

Question 39

quickening

Answer 39

the first recognizable movements of the fetus (e.g. the baby’s kick)

Question 40

antenatal

Answer 40

(from the Latin ante, “before,” natus, “birth”)

occurring before birth; prenatal

Question 41

ultrasound

Answer 41

1: vibrations of the same physical nature as sound but with frequencies above the range of human hearing
2: the diagnostic or therapeutic use of ultrasound and especially a noninvasive technique involving the formation of a two-dimensional image used for the examination and measurement of internal body structures and the detection of bodily abnormalities
— called also sonography
3: a diagnostic examination using ultrasound

An image produce by ultrasound is called a sonogram or ultrasonogram.

Question 42

fetal alcohol syndrome (FAS)

Answer 42

A condition in a child that results from alcohol exposure during the mother’s pregnancy. Fetal alcohol syndrome causes brain damage and growth problems. The problems caused by fetal alcohol syndrome vary from child to child, but defects caused by fetal alcohol syndrome are not reversible.

Question 43

amniotic fluid

Answer 43

the protective liquid contained by the amniotic sac

Question 44

puberty

Answer 44

The process of physical changes through which a child’s body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs.

Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Until the maturation of their reproductive capabilities, the pre-pubertal physical differences between boys and girls are the external sex organs.

Question 45

spermarche

Answer 45

also known as semenarche
the beginning of development of sperm in boys’ testicles at puberty
also refers to the first ejaculation a male ever has

Question 46

spermaturia

Answer 46

a human disease characterized by the presence of sperm in the urine

Question 47

pubarche

Answer 47

the first appearance of pubic hair at puberty

Question 48

viviparity vs. oviparity

Answer 48

Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the mother.

Question 49

thelarche

Answer 49

also known as breast budding
It is the onset of secondary breast development, which often represents the beginning of pubertal development. It is the stage at which male and female breasts differentiate due to variance in hormone levels; however, some males have an abnormal condition in which they develop breasts, termed gynecomastia.

Question 50

gynecomastia

Answer 50

the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogen and androgen

Question 51

androgen

Answer 51

Any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the embryological development of the primary male sex organs, and the development of male secondary sex characteristics at puberty. Androgens are synthesized in the testes, the ovaries, and the adrenal glands.

The major androgen in males is testosterone.

Although androgens are commonly thought of only as male sex hormones, females also have them, but at lower levels: they function in libido and sexual arousal. Also, androgens are the precursors to estrogens in both men and women.

Question 52

estrogen

Answer 52

A category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal activity: estrone (E1), estradiol (E2), and estriol (E3).

In addition to their role as natural hormones, estrogens are used as medications, for instance in menopausal hormone therapy, hormonal birth control and feminizing hormone therapy for transgender women and nonbinary people.

Estrogen levels are significantly lower in males than in females, but nevertheless have important physiological roles in males.

Question 53

primary characteristics vs. secondary sex characteristics

Answer 53

Primary sexual characteristics are present at birth and comprise the external and internal genitalia (e.g., the penis and testes in males and the vagina and ovaries in females).

Secondary sexual characteristics are those that emerge during the prepubescent through postpubescent phases (e.g. breasts enlarging in females)

Question 54

stages of childhood

Answer 54

Childhood is the age span ranging from birth to adolescence.

Childhood is divided up into the developmental stages of infancy (earliest stage of life), toddlerhood (learning to walk), early childhood (play age), middle childhood (school age), and adolescence (onset of puberty).

Question 55

adolescence

Answer 55

a transitional stage of physical and psychological development that generally occurs during the period from puberty to legal adulthood (age of majority)

Question 56

senescence

Answer 56

(1) the condition or process of deterioration with age

(2) loss of a cell’s power of division and growth

Question 57

neonate

Answer 57

a newborn child, especially a child less than a month old

Question 58

dementia

Answer 58

a general term for loss of memory, language, problem-solving and other thinking abilities that are severe enough to interfere with daily life. Alzheimer’s is the most common cause of dementia

Question 59

neonatology

Answer 59

a medical and nursing specialty concerned with the diagnosis and treatment of disorders of the newborn

Question 60

endogenous

Answer 60

1. growing or produced by growth from deep tissue (e.g. endogenous plant roots)
2. caused by factors inside the organism or system
3. produced or synthesized within the organism or system.

Question 61

orthopedics

Answer 61

the branch of medicine dealing with the correction of deformities of bones or muscles