Physiology 🫁 Flashcards
1
Q
what is the male reproductive system composed of?
A
2
Q
what does the testicular parenchyma consist mainly of?
A
- Seminiferous tubules (80%)
- Leydig Cells (20%)
each testis has 700-900 seminefrous tubules
3
Q
what is the function of Gametogenic (spermatogenic) epithelium?
A
responsible for spermatogenesis.
4
Q
what is the location of Leydig Cells = Interstitial cells?
A
between seminiferous tubules.
5
Q
what is the number of Leydig Cells = Interstitial cells?
A
20% of testicular mass
6
Q
when do Leydig Cells appear?
A
- APPEAR at 7-9 th (8th ) week of pregnancy. (temporarily, to form secondary sex organs by HCG)
- At birth They are extensive
- Within first 6 months of postnatal life they disappear.
- At Puberty, they re-appear by differentiation of fibroblast-like cells of testis. (Permenantly, to form testosterone by LH)
7
Q
what do Leydig Cells secrete?
A
- Androgens (testosterone) in fetal life
➥ Under influence of Human Chorionic Gonadotropin (HCG) of placenta.
➥ lead to differentiation of male secondary sex organs (internal & external genitalia).
They also secrete some estrogen
8
Q
what is the structure of Sertoli cells?
The first cell to develop
A
- Large pyramidal.
- non motile.
- non-proliferating tubular cells.
- Lie on basal lamina.
- Extend through entire thickness of germinal epithelium.
9
Q
what is the function of Sertoli cells?
A
Spermiation: Spermiation is the process by which mature spermatids are released from the supporting somatic Sertoli cells into the lumen of the seminiferous tubule. It is a critical determinant of the number of sperm entering the epididymis, and thus the sperm content of the ejaculate.
10
Q
HY antigen
A
11
Q
Notes about spermatogenesis
Spermatogonia (Germinal epithelium) ——–> Spermatozoa (mature sperm)
A
- Occurs in all seminiferous tubules during active sexual life.
- Begins at an average age of 13 years.
- Continue throughout most of remainder of life but decrease markedly in old age. (Unlike females)
12
Q
what are the steps of spermatogenesis?
A
There are 4 phases of spermatogenesis:
1. The type A spermatogonia become enlarged, with large nucleus, granular cytopalsm & thick cell membrane to form 1ry spermatocytes (diploid)
2. 1ry spermatocytes undergoes reduction division (meiosis) to form 2 2ry spermatocytes, each of which contains 23 chromosomes (haploid cells).
3. Each 2ry spermatocytes undergoes mitotic division to form spermatids, which are haploid cells.
4. Transformation of spermatids into spermatozoaby spermiogenesisi.
5. Removal of excess cytoplasm from spermatids by Sertoli cells.
- Production of sperms takes 64 days
- Maturation of sperms takes 10 days
- Storage of sperms takes 12-21 days
13
Q
maturation of sperms
A
- Sperms present in lumen of seminiferous tubules are immature, Non-motile and Non-fertile.
- Maturation occurs in epididymis
14
Q
production of sperms
A
2 testes of human adult form up to 120 million sperm/day.
15
Q
Storage of sperms
A
in vas deferens.
16
Q
what are the factors affecting spermatogenesis?
A
- Hormonal control
- Temperature
- Diet
- Extrinsic factors inhibit spermatogenesis
17
Q
how does Hypothalamic-hypophysial-testicular axis affect spermatogenesis?
A
At puberty, reactivation of hypothalamic LHRH (GnRH) pulse generator occurs resulting in pulsatile secretion of pituitary gonadotropins FSH & LH.
18
Q
what is the effect of FSH related to spermatogenesis?
helps in sperms production directly
A
➥ Maintains gametogenic functions of testes.
➥ ++ growth & secretory functions of Sertoli cells.
➥ Maintains spermatogenic epithelium
19
Q
what is the effect of LH related to spermatogenesis?
gives tst which helps in sperms production
A
+++ Leydig cells to secrete testosterone which is essential for spermatogenesis.
20
Q
how does testosterone affect spermatogenesis?
A
➥ Essential for growth & division of testicular germinal cells.
➥ Essential for spermatogenesis.
21
Q
other hormones and their effect on spermatogenesis
A
GH: ++ early division of spermatogonia.
Thyroid hormone: Essential for spermatogenesis due to their metabolic function. (Provide energy)
22
Q
what is the optimum temperature for spermatogenesis?
A
33-35C (lower than body temp.)
23
Q
what are the factors that keep optimum temperature of testes?
A
How does pampiniform plexus cool down the testis?
- As the veins of the pampiniform plexus climb up the spermatic cord, they surround the testicular artery. In this way, the relatively cool venous blood helps to lower the temperature of the warmer arterial blood in the testicular artery.
24
Q
how does diet affect spermatogenesis?
A
Germinal epithelial atrophy is an end-stage lesion and is generally preceded, or accompanied by, seminiferous tubule degeneration. Depending on severity, the affected testes may be macroscopically flaccid and reduced in size and weight. Severe, diffuse germinal epithelial atrophy is often irreversible.
25
what are extrinsic factors that inhibit spermatogenesis?
26
what is the main hormone secreted from leydig cells?
➥ Testosterone is the major hormone produced by Leydig cells of testis.
27
what is the amount of testosterone in a normal adult male?
A normal adult male secretes 4-9 mg of testosterone daily.
28
what are the physiologic effects of testosterone during fetal life?
**1- Differentiation & development of 2ry male sex organs.** (Of everything but testis)
- Leydig cells of developing testes begin to secrete testosterone at about 7- 9 th week of gestation.
**2- Promotes descent of testes**
- from abdominal cavity into scrotum during last 2 to 3 months of gestation.
29
what are the physiologic effects of testosterone after puberty?
30
what are the metabolic effects of testosterone?
**Protein-anabolic effect leads to:**
i- increased muscle bulk (50 % greater in male than female).
ii- increased bone growth as result of protein-anabolic effect of testosterone plus deposition of calcium salts.
iii- increased thickness of skin & vocal cords.
(Testosterone also causes epiphyses of long bones to unite, therefore preventing overgrowth of long bones.)
"Abscence of Tst may cause increase in length of bones"
**-----------**
**increased basal metabolic rate:**
- usual amounts of testosterone secreted by testes during adolescence & early adult life increase BMR by 5-10%
**-------------**
**Increased RBCs count:**
(average man has about 700,000 more RBCs per cubic mm than average woman)
- This difference may be due to increased metabolic rate rather than direct effect on RBCs production.
"This is the main cause of increase in RBCs in males, not due to menstruation as commonly known"
**---------------**
**Effect on water and electrolytes:**
- Secondary to its anabolic effect, testosterone causes moderate Na+, K+ Ca+ phosphate, sulphate & water retention.
- It also increases size of kidneys.
31
what is semen?
- Semen is the fluid ejaculated at time of orgasm.
- It contains sperms and secretions of seminal vesicles, prostate, Cowper’s glands, and probably, urethral glands.
32
what is male hypogonadism and what are its types?
Impaired testicular functions, primary and secondary
33
what causes primary hypogonadism?
due to testicular disease or certain chromosomal disorders associated with congenital absence of the testes
## Footnote
Castration : removal of testis
34
what causes Secondary hypogonadism?
due to failure of pituitary gonadotropins secretion as in pituitary or hypothalamic diseases.
35
..
36
The definition of puberty
- Physiological transition from childhood to reproductive maturity.
- Puberty is physical and sexual maturation.
37
when does puberty take place?
➥ In Girls: between 8 - 14 years old
➥ In Boys: between 9 - 14 years old.
38
what is puberty associated with?
➥ Growth spurt
➥ Appearance of both 1ry & 2ry sexual characteristics in children.
39
what does Marshall & Tanner staging Reflect?
Reflects progression in changes of external genitalia sexual hair.
40
physical changes in girls during puberty
- **Adrenarche:** activation of adrenal glands.
- **Thelarche** (breast budding) usually 1st sign.
- **Pubarche:** appearance of Pubic & axillary hair (due to adrenal androgens).
- **Growth spurt**
- **Menarche:** after thelarche by 2-3 years.
41
physical changes in boys during puberty
- Puberty in boys begins with testicular enlargement to greater than 2.5 cm in length (9.5 - 14 years of age).
- Pubic hair development in males controlled by both adrenal androgens DHEA as well as testicular androgens, also, axillary and facial hair, and voice changes.
- Male growth spurts typically occur () 11 & 12 years old.
42
Tanner stages in Female
43
what are the factors that influence puberty?
1. Psychological factors (stress).
2. Excessive exercise.
3. Environmental (nutritional status).
4. Genetics (50-80% of variation in pubertal timing).
44
what is considered one of the important hormones that **control onset of puberty**?
an increase in frequency of GnRH pulse stimulation of pituitary.
45
(LH) or (FSH) response to GnRH in prepubertal children
In prepubertal children, no significant (LH) or (FSH) response to GnRH is observed.
46
what happens to (LH) or (FSH) response to GnRH during adolescence?
During adolescence, LH response to GnRH increases progressively in both sexes.
47
which hormone increases more in response to GnRH during puberty, LH or FSH?
LH
48
Describe the way LH and FSH increase in response to GnRH during puberty
- not abrupt but develops over several years
49
what is increase in LH and FSH during puberty evidenced by?
slowly rising plasma concentrations of gonadotropins & testosterone or estrogens.
50
Increase in gonadotropins in girls during puberty
➥ Circulating FSH levels increase progressively from 10 to 11 years of age, approximately 1 year prior to those of LH.
➥ Gonadotropins continue to increase throughout puberty, but important fluctuations are observed in relation to menstrual cycle.
51
Increase in gonadotropins in Boys during puberty
- Significant increase in both plasma FSH & LH is also found from onset of puberty, closely linked to rapid increase in testicular size characteristic of this pubertal stage.
- Further significant increase in circulating gonadotropins is also observed at late pubert
52
what does rise in gonadotropins stimulte the ovary to?
secrete estradiol
53
what are the effects of estradiol?
**Estradiol ++ 2ry sex characters:**
1- Breast development.
2- Reproductive organ growth.
3- Fat redistribution.
4- Bone maturation.
54
when do adrenal androgens start to increase?
Adrenal androgens start to be increased between 8-11 years old. This phenomenon’s called adrenarche.
55
when does Adrenarche begin?
Adrenarche begins before the rise in gonadotropin secretion.
56
what are the actions of adrenal androgens in females?
a- Appearance & maintenance of pubic & axillary hair.
b- Growth of clitoris.
c- Protein anabolism which promotes physical growth in pubertal phase.
d- increased secretion of sebaceous glands of skin leads to acne.
57
Who are the actions of adrenal androgens in males?
have little effects as compared with testicular androgens (testosterone).
58
what happens to GRF levels & GH during puberty?
GRF levels & GH secretion increase considerably during puberty, mainly at night.
59
when does amplitude of GH peak?
Amplitude of GH peaks increase early in puberty.
60
IGF-1
is an important modulator of growth during childhood and adolescence.
61
Effect of insulin in growth and puberty
- is also important for normal growth.
- its rise is particularly during puberty.
62
what results in characteristic pubertal growth spurt?
characteristic pubertal growth spurt results mainly from synergetic effect of gonadal sex steroids, growth hormone, & IGF-I production.
63
Bone growth during puberty
- Both genders experience an increase in bone width followed by mineralization with Ca+2.
64
what causes increased bone fracture during adolescence?
- disparity between increase in size of bone & strength of bone may explain an increase in bone fractures during adolescence.
65
how to avoid bone fractures during adolescence?
Ca+2 intake via dairy products & other sources to maximize bone calcification must be underscored to teenagers.
66
Weight gain during puberty
67
what happens to plasma estradiol levels during puberty?
- Plasma estradiol levels fluctuate widely, probably reflecting successive waves of follicular development that fail to reach ovulatory stage.
68
how is uterine endometrium affected by changes in estradiol levels?
- Uterine endometrium is affected by these changes & undergoes cycles of proliferation & regression, until a point is reached when substantial growth occurs so that withdrawal of estrogen results in 1st menstruation (menarche).
69
what is the level of progesterone in cases of no ovulation with menstruation?
remains at low levels even if 2ry sexual characteristics have appeared.
70
what is the level of progesterone in cases of successful oculation?
Rise in progesterone after menarche is, in general, indicative that ovulation has occurred.
71
when does first ovulation take place? and why?
- 1st ovulation does not take place until 6-9 months after menarche because +ve feedback mechanism of estrogen is not developed.
72
what causes increase in testicular size during pre-puberty & puberty?
development of seminiferous tubules under stimulating effect of FSH
73
what induces differentiation of interstitial cells into testosterone-secreting Leydig cells?
| which, in turn, exert a -ve feedback control on LH secretion.
Long-standing pulsatile LH secretion
74
what sustains spermatogenesis?
FSH and testosterone.
75
what are Normal reproductive years of female, from puberty to menopause, are characterized by?
Characterized by monthly regular changes in rates of secretion of female hormones and corresponding physical changes in ovaries and other sexual organs
76
when do ovarian and menstrual cycles stop?
only during pregnancy or disease
77
what is the average duration of the cycles?
28 days (from 20 to 45 days)
78
what is each ovarian cycle composed of?
Each ovarian cycle is composed of 3 phases:
1) Follicular (pre-ovulatory) phase
2) Ovulatory phase
3) Luteal (post-ovulatory) phase
79
Number of primordial follicles at puberty
At puberty, the two ovaries contain about 400.000 primordial follicles
80
How many Primordial follicle start to grow during each cycle?
During each cycle, about 20 primordial follicles start to grow
81
Formation of primary follicles
- Single layer of follicular cells that cover ovum divides to several layers of granulosa cells
- These follicles are known as primary follicles
82
Development of antral and vesicular follicles (secondary follicles)
**a)** Rapid proliferation of the granulosa cells giving rise to many layers of cells
**b)** Spindle cells derived from ovarian stroma collect in several layers outside the granulosa
cells giving rise to a second mass of cells called theca which is divided into two layers:
1) Theca interna: secrete estrogen and progesterone
2) Theca externa
**c)** After few days, the granulosa cells secrete a follicular fluid that contains estrogen
**d)** Accumulation of this fluid leads to appearance of antrum within the mass of the
granulosa cells. The follicle is now called antral follicle
**e)** Accelerated growth of antral follicles leads to larger follicles called vesicular follicles
83
Formation of the mature follicle (Graafian follicle)
- One of the follicles outgrows all others and other follicles involute and become atretic
- The mature follicle is now called mature Graafian follicle & characterized by presence of:
a) The ovum (secondary oocyte) surrounded with thin membrane called zona pellucida
b) Several layers of granulosa cells surrounding the ovum called corona radiata
c) The antrum containing follicular fluid
d) Several layers of granulosa cells
e) Then surrounded by basal lamina then theca interna & theca externa
84
what is the definition of ovulation?
The release of haploid secondary oocyte into the peritoneal cavity
85
Time of ovulation
In normal 28-day sexual cycle, ovulation occurs 14 days after onset of menstruation
86
How is ovulation diagnosed?
- Symptoms
- Basal body temperature
- Detection of pregnandiole
- Endometrial biopsy
- Examination of cervical mucous
87
Symptoms of ovulation
- Pelvic pain
- Increased vaginal discharge
- Midcycle vaginal bleeding due to sudden drop of estrogen level after ovulation
88
Basal body temperature during ovulation
- On day of ovulation, basal body temperature ↑↑ by 0.2 - 0.5 0C due to the thermogenic effect of progesterone secreted by the corpus luteum
- Elevated basal temperature remains till day 26 of cycle
89
Detection of pregnandiole in ovulation
the progesterone metabolite in urine
90
Endometrial biopsy (Diagnosis of ovulation)
If ovulation occurs, the endometrium will be in the secretory phase
91
Examination of cervical mucous
In preovulatory phase, cervical mucous is characterized by ferning & spinnbarkeit phenomena that disappear after ovulation
**a) Spinnbarkeit phenomenon:** A drop of mucous is placed between two slides, long threads of mucous will appear between them when they are separated
**b) Ferning phenomenon:** A drop of mucous is spread on slide and left to dry, the crystals will be arranged in a feather-like shape
92
what forms the corpus luteum?
- After expulsion of the ovum from the follicle, the remaining granulosa and theca cells enlarge and become filled with lipid material that give them a yellowish appearance and the total mass of cells is called Corpus Luteum
- This process is dependent on LH
93
what is the function of the corpus luteum?
- Corpus luteum secretes large amounts of progesterone (More) & estrogen
- This occurs under control of LH
94
what is the fate of corpus luteum?
**If fertilization doesn’t occur:**
- Called Corpus luteum of menstruation
- It continues to function till day 24 of cycle, then it degenerates
**If fertilization occurs:**
- Called Corpus luteum of pregnancy
- It continues to function till 12th week
of pregnancy by action of human chorionic gonadotropin (HCG), then its function is taken by placenta
95
FSH in Pre-Ovulatory Phase
- In beginning: FSH is high because plasma estrogen is low
- Then: FSH decreases to a low level due to -ve feedback of high estrogen
96
FSH 2 days before ovulation
FSH secretion is increased by 2-3 folds, Due to +ve feedback of high estrogen level on anterior pituitary
97
FSH during post-ovulatory phase
Secretion decreases by -ve feedback of Estrogen high level secreted by corpus luteum
98
what are the functions of FSH?
1. Early growth of ovarian follicles during follicular phase of ovarian cycle
2. Maturation of Graafian follicle (with LH)
3. Stimulates estrogen secretion by granulosa cells of growing ovarian follicles
99
LH in Pre-Ovulatory Phase
- LH secretion is constant (basal) from anterior pituitary
100
LH 2 days before ovulation
LH secretion is increased (LH surge) by 6-10 folds Due to +ve feedback of high estrogen level on anterior pituitary
101
LH in post-ovulatory phase
Secretion decreases by -ve feedback of Progesterone high level secreted by corpus luteum
102
what are the functions of LH?
1. Regulates estrogen secretion from theca interna & granulosa cells of ovarian follicles
2. LH surge is necessary for ovulation, required for corpus luteum formation
3. Stimulates estrogen & progesterone secretion form corpus luteum
103
what is the definition of menstrual cycle?
Occurs secondary to ovarian cycle & consists of cyclic changes that occur in mucosal (inner) layer of the uterus (endometrium)
104
what are the phases of menstrual cycles?
- Bleeding (menstrual or destructive) phase
- Proliferative (pre-ovulatory) phase
- Secretory (post-ovulatory) phase
105
what is the duration of Bleeding (menstrual or destructive) phase?
3-5 days
106
what does **Bleeding (menstrual or destructive) phase** coincide with?
Coincides with follicular phase (first 3-5 days)
107
what happens in **Bleeding (menstrual or destructive) phase**?
- Corpus luteum of preceding cycle degenerates on day 24 of cycle, so ↓↓ estradiol & progesterone levels
- This leads to shedding of functional layer of endometrium
108
How long does menstruation persist?
Menstruation occurs 4 days later as a result of withdrawal of the hormonal support for endometrium
109
what is the type of bleeding in **Bleeding (menstrual or destructive) phase**?
This type of bleeding is called withdrawal bleeding
110
Onset of Proliferative (pre-ovulatory) phase
Follows menstrual phase
111
what does **Proliferative (pre-ovulatory) phase** coincide with?
Coincides with follicular phase (except first 5 days during menstruation)
112
when does Proliferative (pre-ovulatory) phase terminate?
Terminates when ovulation occurs
113
what is teh duration of Proliferative (pre-ovulatory) phase?
9 days, but it is variable depending on duration of menstrual flow & time of ovulation (so variations in length of the cycle are due to changes in duration of this phase)
114
what happens in Proliferative (pre-ovulatory) phase?
Damaged superficial part of endometrium after menstruation is regenerated from the basal layer, This occurs by action of estrogen
115
Onset of Secretory (post-ovulatory) phase
Follows proliferative phase & after ovulation
116
what does Secretory (post-ovulatory) phase coincide with?
Coincides with luteal phase
117
Duration of Secretory (post-ovulatory) phase
Constant at 14 days & after which menstruation occurs
118
what happens in Secretory (post-ovulatory) phase?
Endometrium is prepared for implantation of the ovum (if fertilized) by the effect of estrogen and progesterone secreted by corpus luteum (particularly progesterone) through the following changes:
- Thickening of endometrium (about 6 mm thick)
- Deposition of large quantities of fat, protein and glycogen in the endometrial cells (which will be called decidual cells if pregnancy occurs)
- Endometrium becomes more vascularized
- Spiral arteries reach endometrial surface
- Endometrial glands become tortuous & secrete a clear fluid, so endometrium becomes slightly edematous
119
Hormonal Control of Menstrual Cycle
120
what is the definition of pregnancy?
It’s a physiological condition in a childbearing woman in which a growth of fertilized ovum occur leading to full term baby.
121
duration of pregnancy
38-42 weeks (3 trimesters)
122
mechanism of pregnancy
- At the end of intercourse, about 500 million sperms deposited in the vagina.
- Only, 1000-3000 sperms reach the ampulla of FT where fertilization occurs.
- The first sperm reaches the fallopian tube early within 5-10 minutes because its motility is helped by contractions in the female genital tract due to effect of oxytocin and prostaglandins.
- Sperm remain viable for up to 48 hours within the female reproductive tract.
123
how many sperms are deposited in the vagina at the end of intercourse?
500 million sperms
124
how many sperms reach the ampulla?
1000-3000 sperms
125
when does the first sperm reach the fallopian tube?
within 5-10 minutes because its motility is helped by contractions in the female genital tract due to effect of oxytocin and prostaglandins.
126
for how long do sperms remain viable?
up to 48 hours
127
what is the definition of **Capacitation of the sperm**?
Increase the capacity of the sperm to produce fertilization.
128
how long does it take to capacitate a sperm?
This requires from 1-10 hours in the female reproductive tract.
129
mechanism of capacitation of the sperm
In female reproductive system: the membrane of sperms becomes more permeable to Ca++ which:
1. Increased flagellar movement of tail.
2. Release of proteolytic enzymes from acrosome.
130
what is the site of fertilization?
Outer third of fallopian tube
131
Time of fertilization
14 days after first day of last menstruation
132
steps of fertilization
- Several sperm penetrate corona radiate and attempt to penetrate zona pellucida.
- Sperms bind to sperm receptors.
- Then acrosomal reaction; the breakdown of acrosome and release of hyaluronidase and acrosin.
- One sperm enters ovum and nuclei fuse--producing a zygote.
- Ovum’s plasma membrane and zona pellucida change to prevent polyspermy.
133
What prevents polyspermy?
The fertilization of one ovum by more than one sperm is prevented by :
- The fusion of one sperm to the ovum reduces the membrane potential of the ovum.
- The transient potential changes is followed by structural changes in the zona pellucida that protect against polyspermy.
134
steps of implantation
- The fertilized ovum takes 3-5 days to reach the uterus.
- Then it remains another 3-5 days in the uterus before implantation during which a blastocyst develops and become surrounded by trophoblast.
- At this stage, the blastocyst takes its nutrition from the endometrial secretions.
- At about 7 days after ovulation (and 21 days from the onset of the last menstruation) blastocyst implants cell mass toward endometrium, and secretes enzymes which allow it to penetrate (digest) the endometrium.
135
Formation of the placenta
136
what are the functions of the placenta?
- Respiratory function
- Nutrition & metabolic function
- Excretory function
- Protective function
- Endocrine function
137
Respiratory function of the placenta
O2 diffuses from maternal to fetal blood & CO2 diffuses from fetal to maternal blood according to pressure gradient.
138
nutrition and metabolic function of the placenta
- Water, oxygen, carbon dioxide → simple diffusion
- Glucose → facilitated diffusion
- Amino acids, iron, calcium → active transport
139
Excretory function of the placenta
**E.g. urea, uric acid and creatinine formed in the fetus and diffuse to maternal blood.**
140
protective function of the placenta
- The placenta act as a barrier against the transfer of some harmful substances into the fetus. However some drugs and viruses can cross the placenta causing fetal malformation.
141
endocrine function of the placenta
The placenta secretes the following hormones:
a) Human chorionic gonadotropin (HCG)
b) Estrogen
c) Human chorionic somatomamotropin
d) Progesterone
e) Relaxin.
142
what is the site of release of HCG?
It is a glycoprotein hormone secreted from syncitio- trophoblast
143
Start of secretion of HCG
After one week from fertilization and one day after implantation.
144
Peak of HCG
- 12-16 week of pregnancy
- Decrease to a lower level by 16-20 weeks, and remains constant till the end of pregnancy.
145
Measurment of HCG
In urine and blood
146
what are the functions of HCG?
1. It maintains the function of Corpus Luteum for 12 weeks (secrete estrogen & progesterone to prepare all reproductive system for baby and cause inhibition of FSH and LH from pitutary→ inhibit further ovulation.
2. Stimulates male fetal testis to secrete testosterone (causes the testis to descend into scrotum).
3. Has TSH like action
4. To test for pregnancy
5. Stimulate the secretion of relaxin hormone from placenta.
147
what are the sources of estrogen and progesterone during pregnancy?
- Corpus luteum till 8th week of pregnancy.
- Placenta and corpus luteum between 8th and 12th week.
- Placenta from 12th week till end of pregnancy.
148
plasma levels of estrogen and progesterone during pregnancy
- At the begening of pregnancy, the plasma level of progesterone is low but it increases gradually till the 7th month of gestation then it becomes constant till the end of pregnancy.
149
what are the functions of estrogen during pregnancy?
150
what are the functions of progesterone during pregnancy?
151
nature of Human chorionic somato-mamotropin
It is a protein hormone
152
secretion of Human chorionic somato-mamotropin
its secretion starts at 5th week of gestation then level increase progressively till end of pregnancy.
153
what are the functions of Human chorionic somato-mamotropin?
1. Lactogenic effect but weak compared to prolactin.
2. Has anabolic effect on protein metabolism like growth hormone
3. Mobilize free fatty acids from stores of the mother to spare glucose for fetal tissues (stimulate lipolysis).
154
nature of relaxin
It is a polypeptide hormone
155
secretion of relaxin
secreted by corpus luteum and placenta.
156
what are the functions of relaxin?
1. Relaxation of the pelvic ligaments & joints.
2. Soften the cervix at the time of the labour.
3. Inhibtion of uterine contractions.
157
- what are other hormonal changes during pregnancy?
- Pituitary gland hormones
- Corticosteroids
- Thyroid hormones
- Parathyroid hormone (PTH)
158
hormonal changes in pituitary gland hormones during pregnancy
- The secretion of ACTH, TSH and prolactin increases.
- The pituitary secretion of FSH and LH is suppressed as a result of the inhibitory effects of estrogens and progesterone from the corpus luteum and the placenta.
159
change in corticosteroids during pregnancy
- The rate of secretion of glucocorticoids is moderately increased to help mobilization of amino acids from the mother’s tissue to the fetus.
- Aldosterone secretion is also increased, this leads to sodium and water retention.
160
changes in thyroid hormones during pregnancy
- Thyroid hormone secretion is increased due to the thyrotropic effect of HCG and human chorionic thyrotropin secreted by the placenta.
161
changes in parathyroid hormone during pregnancy
- Increased PTH secretion leads to mobilization of calcium form the mother’s bones to supply sufficient calcium to the fetus.
162
what is the definition of labour?
- Labour is the physiological process by which a well-developed fetus is expelled from the uterus to the outside world.
163
what is the time of labour?
- Usually 270 days after fertilization, 284 days from the first day of the menstrual period preceding pregnancy.
164
what hormones take place in hormonal mechanism of labour?
- Estrogen / progesterone ratio
- Oxytocin
- Relaxin
- PGs
165
Estrogen / progesterone ratio in labour
- Progesterone : decraeses uterine contraction during pregnancy
- Estrogen : increases uterine contraction during pregnancy
- After the 7th month : progesterone decrease & estrogen increase markedly leading to increased uterine contractions and initiation of labour.
166
Oxytocin role in labour
- During early labour : oxytocin level is normal but estrogen increases its receptors.
- Once labour starts: Uterine contractions causes dilatation of cervix causing stimulation of stretch receptors, send impulses to posterior pituitary, that increases oxytocin which by its turn increases uterine contractions.
167
Relaxin role in labour
- It relaxes pelvic joints & softens & dilates the cervix and facilitation of passage of fetus during labour.
- Since it inhibits uterine contractions , its secretion is decreased in last days of pregnancy allowing labour to occur.
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PGs role in labour
- They are secreted at the end of pregnancy from uterus & fetal membranes.
- They increases uterine contractions.
- Secretion is stimulated by estrogens and oxytocin
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what is the role of CRH (cortico-tropin hormone) in labour?
The first step that initiates labor may be the significant increase in fetal CRH which results in:
1. Increase Cortisol secretion and maturation of respiratory tract.
2. Increase estrogen secretion that stimulate contractions by:
a) Increase receptors for oxytocin.
b) Increase gap junction between myometrial cells.
c) Increase prostaglandins.
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mechanical factors that help in labour
1. Stretch of the cervix by the head of the baby leads to reflex contraction of uterus and impaction on head into cervix i.e. more stretch and reflex contraction & so on.
2. Cervical stretch also stimulates pituitary gland to secrete oxytocin which increases uterine contractility.
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development of mammary glands during childhood
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development of mammary glands at puberty
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development of mammary glands during pregnancy
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what is the role of estrogens on breast?
1- Enlargement of the breasts due to fat deposition.
2- Increased vascularity.
3- Growth of the duct system and nipple. **MCQ**
4- Pigmentation of the areolas.
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what is tne role of progesterones on breast?
- Stimulates growth of the lobules and secretory alveoli which become lined with secretory cells. **MCQ**
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what is the role of prolactin on breast during pregnancy?
- The hormone level rises steadily from **5th week of pregnancy** onwards.
- The **high estrogens** blood level present during pregnancy **stimulates its secretion**, but **blocks its lactogenic effect** on the mammary glands.
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what is the role of prolactin on breast after labor?
- **Sudden loss of both estrogen & progesterone from the placenta** allows the **lactogenic effect of prolactin** from the mother’s pituitary gland to **start its natural milk-secreting role.**
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what is the role of prolactin on breast after birth?
- **Basal level of prolactin** secretion **returns** during the **next few weeks** to non-pregnant level.
- However, **each time the mother nurses her baby;** **nerve impulses** from nipples to hypothalamus cause a **ten fold surge in prolactin** secretion which **lasts about one hour.**
- It acts on breasts to **provide milk for the next nursing period.**
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what is the role of oxytocin on breast?
- **Milk ejection** is produced by **oxytocin** which causes contraction of **myoepithelial cells** that surround the alveoli and fine ducts, thus **squeezing the milk** outwards through the nipples
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what causes **Full development of the mammary glands?**
by the effects of the high levels of **estrogens, progesterone, prolactin and human chorionic somatomammotropin**
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Roles of Estrogen, Progesterone, Prolactin, Prolactin (PRL) in full development of mammary glands
182
what happens to prolactin levels during pregnancy?
PRL levels increase 20 fold but action of PRL inhibited by high E & P levels
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Role of Human chorionic somatomammotropin (i.e. placental lactogen) in lactation
plays role in lactogenesis.
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Milk production (Towards the end of pregnancy)
**breasts are fully developed but milk production is suppressed except for small amount of colostrum (same concentration of proteins and lactose as regular milk but hardly any fat).**
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what does Separation and expulsion of placenta lead to?
(Concerning estrogen levels & prolactin)
reduction in circulation of estrogen and progesterone resulting in release of prolactin by anterior pituitary gland.
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- Estrogen suppresses action of prolactin
- promotes production of milk 3 days after delivery after allowing adequate amounts of circulating prolactin.
..
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what cells do prolactin act upon?
Prolactin acts on the acini-milk producing cells
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which hormone could cause suppression of milk?
- Thus if suppression of milk is required estrogen can be administered.
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what does oxytocin stimulate?
- Oxytocin stimulates milk secretion and is released during the ‘let down’ or milk ejection reflex.
- After let down, milk travels into the ductules, then to the larger lactiferous or mammary ducts.
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Which hormone is increased by nipple stimulation?
Prolactin levels rise with nipple stimulation.
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what cells make milk in response to prolactin?
- Alveolar cells make milk in response to prolactin when the baby sucks.
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what is the definition of **Milk secretion**?
Milk synthesis is an active process.
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what is **Milk secretion** stimulated by?
1. Anterior pituitary hormones: prolactin, ACTH and TSH.
2. Human chorionic somatomammotropin: supplements prolactin action.
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reflexes of **Milk ejection (lactation)**
- Unconditioned reflex (suckling reflex)
- Conditioned reflex
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Unconditioned reflex (suckling reflex)
- **Impulses initiated by touching the nipple and areola** during nursing.
- **Stimulate hypothalamic nuclei**, mainly paraventricular nucleus, which **send impulses** to **posterior pituitary** leading to **release of the stored oxytocin**.
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Conditioned reflex of suckling
The mother can stimulate milk ejection due to release of oxytocin on :
1- Seeing her baby.
2- Hearing his crying
3- Thinking at him.
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Neuro-hormonal reflex (suckling or let down reflex)
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what inhibits suckling reflex?
Suckling reflex is inhibited by fear , pain and ebarresement, Therefore ensure pain free during Breastfeeding.
