Mod 3, Human Development

Question 1

zygote

Answer 1

The union of sperm and egg to form a diploid
zygote

Question 2

external vs internal fertilization

Answer 2

External fertilization - sperm and egg unite
outside bodies of the parents
- Sperm and eggs released into water
(spawning) and the sperm swim to reach the
eggs.
2. Internal fertilization - occurs within female’s
body, sperm placed within female’s reproductive
tract, where the egg is fertilized
In some animals, such as earthworms and many
snails, single individuals produce both sperm
and eggs

Question 3

hermaphrodites

Answer 3

In some animals, such as earthworms and many
snails, single individuals produce both sperm
and eggs
- Such individuals are called
hermaphrodites

Question 4

zygote chromosomes

Answer 4

Male and female gametes (sperm and egg) join to form a single cell (zygote);
 Zygote contains total of 46 chromosomes, (23 from each parent);
 Carry out Internal Fertilization, within the female body;
 Usu. occurs by copulation, male deposits sperm directly into female’s reproductive
tract
 Animal development begins with a single cell that multiplies and changes to form a
complete organism

Question 5

sperm cell 3 parts

Answer 5

head, middle piece and tail
* The head contains a nucleus caped by a membrane-bounded acrosome

Question 6

Egg/Ovum

Answer 6

Plasma membrane surrounded by thin clear layer of protein and carbohydrates, zona
pellucida.
* zona pellucida surrounded by several layers of adhering follicle cells called corona
radiata.
* Provide nourishment for the egg.

Question 7

how does sperm travel by vagiba?

Answer 7

Exit male urethra during Ejaculation;
oEnters female’s vagina during intercourse;
o Travels to cervix»_space;>through uterus
»oviduct
oMany sperm do not survive this journey,
some goes wrong way or destroyed by
acidic environment of vagina

Question 8

Egg

Answer 8

One egg released from ovary and swept
into an oviduct;
 Egg move towards uterus (4 days) by
muscular contraction and cilia action;
 Egg must be fertilized within 12-24 hrs.

Question 9

window of egg fertiliZation

Answer 9

12-24 hrs

Question 10

stages of fertilization

Answer 10

Fertilization in Humans
Stages of fertilization
1. Sperm squeezes through corona radiata;
2. Sperm releases acrosomal enzymes to
penetrate the zona pellucida;
3. Sperm moves ahead via lashing action of its
tail;
4. Sperm cell membrane fuses with egg cell
membrane
5. Sperm enters egg, nucleus is released
- Once a sperm enters an egg, egg membrane
prevents other sperm from entering.
6. Membranes of the sperm nucleus and egg
nucleus disappear.
Resulting single cell is called a new life, Zygote.

Question 11

Polyspermy

Answer 11

more than one sperm penetrate the egg

Question 12

how does the egg prevent binding of any other sperm?

Answer 12

egg’s plasma membrane depolarizes (from -65mV to 10 mV),
and prevents binding of any other sperm
 In addition, the zona pellucida lifts away from egg’s surface
which prevents sperm from binding

Question 13

consequences of Polyspermy

Answer 13

— Would result in abnormal chromosome number with abnormal
development

Question 14

development, indirect vs direct development

Answer 14

Indirect development
(invertebrates): newborn
has a very different body
structure than the adult
direct development: Direct development:
miniature versions of the
adults of their species.

Question 15

3 principal processes of development

Answer 15

cell division: Individual
cells multiply
differentiation: Daughter
cells
differentiate
organization: As cells
differentiate,
they become
organized
into
multicellular
structures

Question 16

Direct Development

Answer 16

Newborns are typically larger
than indirectly developing species
b. Few offspring are produced, but
they are more developed
i. They also require more nourishment
ii. Many species produce eggs, which
contain yolk to nourish the developing
embryo.
Occurs in fish, amphibians, and all mammals and
reptiles

Question 17

indirect developmenmt

Answer 17

The newborn has a very different body
structure than the adult.
a. Large numbers of eggs are produced
that have a small yolk
b. An immature larva emerges from the
egg
c. Metamorphosis produces a sexually
mature adult
Occurs in most amphibians and most
invertebrates

Question 18

embryonic development/cellular differentiation

Answer 18

Embryonic Development:
- takes place during 1st 2 months
- Involves development of major
organs.
2. Cellular Differentiation/Fetal period of
development:
- Takes place during months 3-9
- Involves refinement of organ
systems

Question 19

embryonic vs fetal period

Answer 19

embryonic: first 8 weeks, organs are taking shape, morphogenesis
fetal: 9th week until birth, organs continue to develop, growth and refinement of structures

Question 20

developmnent in embryonic period

Answer 20

1. Cleavage of Zygote
   – Mitotic cell division
   of fertilized egg
2. 2. Implantation – Cells
      secrete digestive
      enzymes to burrow
      into endometrium
3. 3. Gastrulation –
      formation of three
      tissue layers
4. 4. Organogenesis -
      Major body parts
      develop

Question 21

cleavage

Answer 21

Zygote undergoes cleavage as it migrates through uterine tube toward
uterus:
 Increases no. of cells but not total volume of cytoplasm;
 Divisions of zygote are equal;
 Forms a multicellular stage called a Morula (spherical ball of 16
cells);
 Morula reaches uterus within 3-5 days after fertilization;

Question 22

Blastocyst

Answer 22

Morula cells become filled with fluid»_space; form
spherical structure, Blastocyst (5 days);
 Blastocyst is a hollow ball of cells and has
two (2) diff. cell types:
 Outer layer of cells, trophoblast
adhere to the uterus»_space;> becomes
the Chorion
 Inner layer of cells, inner mass cells
»>becomes the embryo.

Question 23

Trophoblast

Answer 23

secretes enzymes - digest tissues
and blood vessels of endometrium

Question 24

Implantation

Answer 24

Blastocyst burrows itself into uterine wall,
Implantation.

Question 25

implantation process

Answer 25

Implantation  Completed by 10th to 14th day;  Successful implantation = Pregnancy;  Upon implantation, trophoblast secrete Human Chorionic Gonadotropin (hCG):  hCG has same function as LH and maintains corpus Luteum;  Secretion of estrogen and progesterone continues >>>maintain endometrium and prevent menstruation;  High levels of hCH continues for only 2 mths,  placenta secretes estrogen and progesterone to main endometrium and prevent ovulation

Question 26

Gastrulation

Answer 26

cells forms three tissue layers (ectoderm, endoderm and mesoderm) and move to destination

Question 27

Amniotic Cavity

Answer 27

Amniotic Cavity forms between inner mass of cells and trophoblast;  Inner cell mass flatten, called embryonic disk;  Initially, embryonic disk consists of two layers: Ectoderm (outer) and Endoderm (inner);

Question 28

mesoderm

Answer 28

Another layer, mesoderm forms between endoderm and ectoderm, Gastrulation

Question 28

Morphogenesis

Answer 28

development of distinct structures, embryonic cells become different cell types, differentiation.

Question 29

cells in the endoderm, ectoderm, and mesoderm

Answer 29

cells that will line digestive tract, respiratory tract, liver and pancreas are called endoderm; - cells that will form structures such as skin, hair, and nails, and nervous system are called ectoderm; - cells that will forms structures such as muscles, skeleton, and circulatory system are called mesoderm.

Question 30

Notochord

Answer 30

Embryonic tissues transformed into body’s organs and human shape;  mesoderm cells develop along back of embryonic disk form rod- like structure called the Notochord; Nervous system develops above notochord:

Question 31

neurulation

Answer 31

mesoderm cells develop along back of embryonic disk form rod- like structure called the Notochord;  Nervous system develops above notochord:  Cells above notochord surface thickens and develops folds on each side;  Folds fuse to form a tube which then develops into brain and spinal cord, Neurulation.

Question 32

Pre-Natal Development week 1-7

Answer 32

1st week - Cleavage and Implantation * 2nd week - Gastrulation * 3rd week – Neurulation * 4th -8th weeks – Organ formation: * 4th week: formation of blood cells and blood vessels, lungs and kidneys shape is formed, distinct head and evidence f eyes, ears, nose, embryo is 0.6cm. * 5th week: eyes opened, brains cells differentiating, embryo is 1.3cm. * 6th week: limbs lengthen and flex, gonads start producing hormones. * 7th week: distinct human characteristics, all organs are formed and nervous system co-ordinates body activities

Question 33

first week embryonic period

Answer 33

Fertilization occurs within distal third of a uterine tube;  zygote undergoes first cleavage divisions and migrates through uterine tube toward uterus;  After ≈ three days it is in the morula stage.  Morula enters uterus  At day five it becomes a blastocyst — Outer layer of trophoblast cells becomes the chorion — The inner cell mass becomes the embryo.

Question 34

second week of embryonic development period

Answer 34

Implantation begins as trophoblast cells secrete digestive enzymes to burrow into the endometrium.  Trophoblast cells begin to secrete human chorionic gonadotropin.  inner cell mass detaches itself from the trophoblast. — Two more extraembryonic membranes form — Amnion and yolk sac develop below embryonic disk  Gastrulation occurs – the inner cell mass now becomes the flattened embryonic disk. — At this stage ectoderm and endoderm differentiate

Question 35

third week of embryonic period

Answer 35

The nervous system becomes visually evident.  The neural folds meet at the midline; the neural tube will later develop into the brain and spinal cord.  Development of the heart begins.  At first there are right and left heart tubes.  After the tubes fuse, the heart begins pumping blood.

Question 36

fourth/fifth week embryonic development

Answer 36

The body stalk (mesoderm) connects the caudal (tail) end of the embryo with the chorion.  The chorion has tree-like projections called chorionic villi.  The fourth extraembryonic membrane (allantois) is contained within the stalk. — Its blood vessels become umbilical blood vessels. — The umbilical cord forms which connects the embryo to the placenta.  Limb buds appear  Sense organs are distinguishable

Question 37

The sixth through eighth weeks

Answer 37

The embryo becomes recognizable as a human. — The head achieves its normal relationship to the body. — The nervous system continues to develop.  Reflexes are present. — All organ systems are now established even though the embryo weighs les

Question 38

week 12 development

Answer 38

The neck is well defined; all organs are present; distinctly male or female external genitals are present; arms and legs move; teeth begin to form; a heartbeat can be detected.

Question 39

week 16

Answer 39

Sucking and swallowing movements occur; the liver and pancreas begin functioning. The body has grown relative to the head; major organs continue developing. The mother may feel movement; weight is about 5 oz.

Question 40

week 20 and 24

Answer 40

-The fetus may suck its thumb; arms and legs can punch and kick; the body can change position. Fingernails are formed; fat is deposited under the skin; eyebrows and eyelashes appear. -Brain development continues, hearing develops, and the eyes can move. The fetus can hiccup, squint, smile, and frown. The fetus may have hair on its head. Unique foot- and fingerprints appear. Weight is about 11.5 lbs

Question 41

week 30 and 36

Answer 41

week 30: Brain development continues; the eyes open and close and see light; the fetus kicks and stretches. Breathing movements occur but the lungs are not mature. Bones are present but flexible. The baby may survive if born week 36: Eyes open and close corresponding to wake and sleep cycles; body fat increases; lungs and other organs are functional. The fetus can grasp and orient toward light. Weight is about 56 lbs, and the child is no longer considered premature if born. Full term is 38 weeks

Question 42

function of placenta, umbilical cord, and membranes

Answer 42

Together with Placenta and Umbilical Cord, membranes provide protection, nutrition, respiration and excretion. *Expelled from uterus and collectively called, afterbirth.

Question 43

amnion

Answer 43

transparent sac that develops from cells of the embroyonic disk; grows it enclose the mebryo completely; penetrated only by the umbilicial cvoird, filled with amniontic fluid , protects mebryo from trauma and temperature fluctuations

Question 44

yolk sac and allantois

Answer 44

a small sac that s suspended from the abdominal area of the embryo, it contirbutes to the formation of the digestive tract and produces the first blood ce/future egg or sperm cells: NO NUTRITIVE function allantois: forms the foundation for the umbilical cord, dyuring the second monthg, most of it degenerates: becomes the urinary bladder from what is left behind

Question 45

chorion

Answer 45

outermost membrane,m encloses all other extra embryonic membranes

Question 46

Placenta

Answer 46

attached to uterine wall by allantois and chorionic villi.  The placenta is fully formed by tenth week.  Produces progesterone and estrogen  Functions in gas, nutrient, and waste exchange between the fetal and maternal circulatory systems  Fetal and maternal blood do not mix  Gas exchange occurs through chorionic villi

Question 47

Umbilical cord

Answer 47

take fetal blood to and from the placenta.  Harmful substances (ex: alcohol, some medications) can cross the placenta and cause irreversible birth defects.

Question 48

1st, second, third trimester

Answer 48

First Trimester (wk. 1 to 12)  Embryonic period of development;  Cartilage-based skeleton harden and development of bone.  External reproductive organs visible and growth in body length. Second Trimester (wk. 13 to 24)  Strong heartbeat and rapid growth of brain;  Formation of bones in skeleton and movement can be felt;  Nervous system function and fetus covered with fine, soft hair, Lanugo;  Skin covered with a thick, coating, vernix caseosa and become filled with blood vessels. Third Trimester (wk. 25 to 38)  Brain cells multiply rapidly;  Layer of fat develop below skin and testes in males descends into scrotum.

Question 49

symptom begin pregnancy

Answer 49

Morning Sickness and Energy Level  Nausea, vomiting, loss of appetite, and fatigue may be experienced about six weeks into pregnancy. — symptoms usually subside by the twelfth week. — Subsequently, some mothers feel more energetic or have a general sense of well-being.  Weight gain due to breast and uterine enlargement, fetal weight, amniotic fluid, size of placenta.

Question 50

events occuring shortly before birth

Answer 50

During the last trimester - Contractions occur light at first (15 to 20 minutes) but become stronger toward the end of pregnancy. Events that occur shortly before birth  Strong uterine contractions occur about every five minutes.  “water breaks” – amnion has ruptured and amniotic fluid is released.  A mucus plug (from the cervix) is expelled. — plug prevents bacteria and sperm from entering the vagina during pregnancy.

Question 51

Parturition

Answer 51

Parturition is the process of birthing and divided into three (3) stages: Dilation Stage, Expulsion Stage and Placental Stage. 1. Dilation Stage (2-20hrs.): - Contraction of uterine muscles and oxytocin causes cervix to open; - Amniotic sac breaks to release amniotic fluid. 2. Expulsion Stage (0.5 – 2hrs.): - Contraction forces baby through cervix to birth canal; - Head rotates to make it easier to pass through.

Question 52

Placental Stage:

Answer 52

Placental Stage: - Placenta and umbilical cord expelled from uterus 10-15 mins after baby is born; - Expelled placenta called the afterbirth.

Question 53

hormonal control of parturition

Answer 53

1. estradiol fromn the placenta readies the uterus for a response to oxytocin 2. the fetus's head pushing against the cervix activates stretch sensitive sensory neurons that send stimulatory signals to the mothjer's hypothalamus 3. hypothalamus stimulates secretion of oxytocin from the posterior pituitary gland 4. oxytocikn stimulates stronger uterine contractions 5. prostaglandins secreted by the uterus also enhance contractions

Question 54

Caesarean

Answer 54

Incision made by physician in mother’s abdomen and uterus; - Baby delivered through incision;

Question 55

milk secretion

Answer 55

Milk secretion is stimulated by the hormones of pregnancy.  Each breast contains 15-25 lobules.  Each lobule has a milk duct which branches from the nipple into mammary glands;  The human female breast consists of milk-producing mammary glands embedded in fatty tissue and connected to the chest wall by ligaments  During pregnancy, estrogen and progesterone, stimulate mammary glands to swell.  The mammary glands consist of clusters of hollow milk-producing glands, called alveoli, arranged in a circle around the nipple, each with a milk duct leading to the nipple

Question 56

Prolactin

Answer 56

stimulates milk synthesis:  Inhibited by estrogen and progesterone during pregnancy  When placenta is delivered, the anterior pituitary produces prolactin

Question 57

colostrum

Answer 57

First secretions are colostrum, which is rich in protein and antibodies

Question 58

lactation/suckling reflex

Answer 58

oxytrocin: causes milk let down reflex prolactin: causes rapid milk production for the next feeding 1. suckling stimulates nerve endings in nipple and areaola of breast 2. enural pathways carry stimuli to hypothalamus 3. hypothalamus produces oxytocin that is released by posterior pituitary 4. oxytocin causes m,ammary lobules to cojtract

Question 59

for developmental weeks

Answer 59

BIT-M IG-HAY NNH C4C HUMAN! HEARTBEAT IN VAGINA MOVING HEAR? SURVIVE? FAT?

Question 60

3 male accessory structures

Answer 60

. The Seminal Vesicles (60% of fluid); 2. The Prostate Gland (30% of fluid); 3. The Bulbourethral/Cowper’s glands.

Question 61

compare male/female gamete 4 main steps of embroyonic period

Answer 61

Male gamete (sperm): Small in size Motile (has a flagellum/tail) Produced in large numbers continuously Contains very little cytoplasm No stored nutrients Can carry either an X or Y chromosome Lives about 48–72 hours in the female reproductive tract Female gamete (ovum/egg): Large in size Non-motile Usually one released per month Contains a large amount of cytoplasm Stores nutrients for early development Carries only an X chromosome Lives about 24 hours after ovulation

Question 62

3 types of embroynic tissue

Answer 62

Ectoderm – forms the skin (epidermis), hair, nails, and the nervous system. Mesoderm – forms muscles, bones, connective tissue, blood, heart, and kidneys. Endoderm – forms the lining of the digestive and respiratory systems, plus organs like the liver and pancreas.

Question 63

4 stages of childbirth

Answer 63

dilation expulsion placental ?????

Question 64

4 m,ain steps of embryonic period

Answer 64

1st week - Cleavage and Implantation * 2nd week - Gastrulation * 3rd week – Neurulation * 4th -8th weeks – Organ formation--organogenesis

Question 65

sequence of events sperm penetrating egg

Answer 65

1. sperm squeezes through corona radiata ' 2. releases acrosomes top break throiugh zona pellucida 3. Tails lash --move ahewwad to join with egg 4. sperm enters egg: Nucleus released from sperm 5. Membranes disapear 6. joins

Question 66

what cells produce the notochord

Answer 66

mesoderm cells

Question 67

function of hcg

Answer 67

maiontains lh, which maintains the corpus luteam

Question 68

when is the placenta fully formed by

Answer 68

week 10

Question 69

when do testes in males descend

Answer 69

3rd trimester

Question 70

alveoli

Answer 70

The mammary glands consist of clusters of hollow milk-producing glands, called alveoli,

Question 71

waht is prolactin inhibited by

Answer 71

estrogen/progesterone

Question 72

percent of sperm in fluid

Answer 72

5%

Question 73

semen

Answer 73

sperm + other fluids

Question 74

3 functions of female reproductive system

Answer 74

accept sperm, conduct sperm to egg, noursih the developing embryo

Question 75

proliferative phase, secretory phase, menustration

Answer 75

Follicle maturation occurs. Estrogen secretion is prominent Proliferative phase- Days 6-13**** endometrium rebuilds with estrogen LH secretion continues. Corpus luteum forms Secretory phase- Days 15-28= progesterone both the same: uterine cycle: secretory cycle ovarian cycle: luteal LH secretion continues. Corpus luteum forms Secretory phase- Days 15-28= progesterone uterus menstrual: 1-5 proliferative: day 6-13 secretory day 15-28 ovaries folliclur 1-13 ovulation day 14 day 15-28 luteal

Question 76

why does the tail of the sperm drop off

Answer 76

not needed, the nucleus and acrosome is what is needed

Question 77

genome

Answer 77

specific number of chromosomes in that organism: tyhats why we could only mate with the same species = only way to produce viable offspring

Question 78

depolarization of egg

Answer 78

-65mv to +10 mv

Question 79

cells that form embronic disk

Answer 79

inner mass cells form GERM LAYERS=EMBRYONIC DISC

Question 80

location of amniotic cavity

Answer 80

between inner masss of cells and trophobblasts

Question 81

start of morphogenesis

Answer 81

gastrulation

Question 82

blastoful

Answer 82

where gastrulation starts

Question 83

CHARACHTERISTIC OF ALL VETEBRATES

Answer 83

notochord=which provides framework for the development of the nervous system

Question 84

extraembryonic structures

Answer 84

allantois, placenta, chorion, yolk sac, chorionic villi, umbilicial cord (body stalk and yolk stalk)

Question 85

week that eyes open

Answer 85

5

Question 86

week that kidneys/lungs formed

Answer 86

4

Question 87

weeks that ALL organs are established

Answer 87

6-8

Question 88

chorion

Answer 88

forms the fetal portion of the placenta

Question 89

when does cartilage harden

Answer 89

1st trimester

Question 90

symptoms result from

Answer 90

progesterone/estrogen

Question 91

teratogens example

Answer 91

Alcohol: Causes Fetal Alcohol Spectrum Disorders (FASD). Nicotine/Smoking: Causes low birth weight and preterm labor.

Question 92

cells in uterus needed for contractions

Answer 92

mechanoreceptors

Question 93

cervical stretching

Answer 93

triggers hypothalamus=trigegrs posterior pituitary to release oxytocin

Question 94

estradiol

Answer 94

prepares the uterus to respond to oxytocin

Question 95

lobule

Answer 95

breast, each one has a milk duct

Question 96

estrogen and progesterone during pregnancy

Answer 96

stimulate mammary glands to swell

Question 97

what contractsx to produce milk

Answer 97

lobules