Lecture 7 - Female Reproductive System:Structure of organs and Duct System ( Part 2 ) | Animal Physiology and Functional Histology- I - MBBS PDF Download

 Page 1


Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
30 
Fig. 17: Vasculature of Human uterine endometrium. 
Source: ILLL in house 
Cyclic Changes in the Endometrium   
Both the structure and function of the endometrium, including the epithelium, lamina 
propria, glands and blood vessels are subjected to the influence of ovarian steroid hormones 
(Figure 18). Generally, three stages of cellular reorganization are observed during each 
menstrual cycle.  
These are 1) a proliferative phase, 2) a secretory phase, and 3) a menstruation 
phase. During the estrous cycle the uteri also undergo progressive enlargement and 
become distended owing to the accumulation of luminal fluid (next chapter).  
The endometrium of the uterus undergoes pronounced cyclical changes every month during 
a woman’s reproductive years (Figure 18). These changes consist of a gradual building of 
tissue in preparation for receiving a fertilized egg followed by abrupt breakdown of this layer 
and a menstrual flow if pregnancy does not occur.  The endometrial and superficial 
connective tissue layers of the uterine lining are at their maximum height (nearly 6-mm) 
during the fourteenth to twenty-sixth days of menstrual cycle.  At this time, the endometrial 
glands are well developed and secrete a fluid that nourishes the embryo.  Therefore, this 
period is referred to as the secretory phase.  There are abundant blood vessels present in 
the superficial layer of endometrium at this stage.  These are elongated and follow a spiral 
course as they extend from the basal portion to the surface epithelium.  If no pregnancy 
occurs, drop in estrogen and progesterone levels makes the terminal portions of these 
vessels constrict.  This deprives the superficial layers of the uterine lining of a supply of 
oxygen (ischemia) and results in their degeneration.  About two days after the 
vasoconstriction takes place, the affected parts of the uterine lining begin to shed resulting 
in bleeding called the menstrual flow.  This constitutes the menstruation phase.  The 
menstrual fluid consists of epithelium, connective tissue, and blood.  This blood normally 
clots in the uterus and the clots are broken up by enzyme action before flowing from the 
cervix. However, if menstruation at any given time is abnormally rapid, the blood may clot 
in the vagina.  The normal blood loss during a menstrual period is variable, with an average 
of about 50 ml.  Menstruation normally takes four days, with an average of three to six 
days.  At this stage, the endometrium is only about 1 mm thick (Figure 10).  It goes in to a 
three-day repair phase during which i) continuity of the epithelium is re-established, ii) the 
Page 2


Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
30 
Fig. 17: Vasculature of Human uterine endometrium. 
Source: ILLL in house 
Cyclic Changes in the Endometrium   
Both the structure and function of the endometrium, including the epithelium, lamina 
propria, glands and blood vessels are subjected to the influence of ovarian steroid hormones 
(Figure 18). Generally, three stages of cellular reorganization are observed during each 
menstrual cycle.  
These are 1) a proliferative phase, 2) a secretory phase, and 3) a menstruation 
phase. During the estrous cycle the uteri also undergo progressive enlargement and 
become distended owing to the accumulation of luminal fluid (next chapter).  
The endometrium of the uterus undergoes pronounced cyclical changes every month during 
a woman’s reproductive years (Figure 18). These changes consist of a gradual building of 
tissue in preparation for receiving a fertilized egg followed by abrupt breakdown of this layer 
and a menstrual flow if pregnancy does not occur.  The endometrial and superficial 
connective tissue layers of the uterine lining are at their maximum height (nearly 6-mm) 
during the fourteenth to twenty-sixth days of menstrual cycle.  At this time, the endometrial 
glands are well developed and secrete a fluid that nourishes the embryo.  Therefore, this 
period is referred to as the secretory phase.  There are abundant blood vessels present in 
the superficial layer of endometrium at this stage.  These are elongated and follow a spiral 
course as they extend from the basal portion to the surface epithelium.  If no pregnancy 
occurs, drop in estrogen and progesterone levels makes the terminal portions of these 
vessels constrict.  This deprives the superficial layers of the uterine lining of a supply of 
oxygen (ischemia) and results in their degeneration.  About two days after the 
vasoconstriction takes place, the affected parts of the uterine lining begin to shed resulting 
in bleeding called the menstrual flow.  This constitutes the menstruation phase.  The 
menstrual fluid consists of epithelium, connective tissue, and blood.  This blood normally 
clots in the uterus and the clots are broken up by enzyme action before flowing from the 
cervix. However, if menstruation at any given time is abnormally rapid, the blood may clot 
in the vagina.  The normal blood loss during a menstrual period is variable, with an average 
of about 50 ml.  Menstruation normally takes four days, with an average of three to six 
days.  At this stage, the endometrium is only about 1 mm thick (Figure 10).  It goes in to a 
three-day repair phase during which i) continuity of the epithelium is re-established, ii) the 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
31 
remaining blood vessels start to grow upward again, and iii) development of glands is 
initiated as invaginations of epithelium.  Rapid growth of the epithelium, blood vessels, and 
connective tissue takes place during the next week.  This is called the proliferative phase.  
It is followed by another secretory phase.  All these changes are closely timed with those 
occurring in the maturing follicle of the ovary. 
 
 
 
 
 
 
 
 
 
 
Page 3


Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
30 
Fig. 17: Vasculature of Human uterine endometrium. 
Source: ILLL in house 
Cyclic Changes in the Endometrium   
Both the structure and function of the endometrium, including the epithelium, lamina 
propria, glands and blood vessels are subjected to the influence of ovarian steroid hormones 
(Figure 18). Generally, three stages of cellular reorganization are observed during each 
menstrual cycle.  
These are 1) a proliferative phase, 2) a secretory phase, and 3) a menstruation 
phase. During the estrous cycle the uteri also undergo progressive enlargement and 
become distended owing to the accumulation of luminal fluid (next chapter).  
The endometrium of the uterus undergoes pronounced cyclical changes every month during 
a woman’s reproductive years (Figure 18). These changes consist of a gradual building of 
tissue in preparation for receiving a fertilized egg followed by abrupt breakdown of this layer 
and a menstrual flow if pregnancy does not occur.  The endometrial and superficial 
connective tissue layers of the uterine lining are at their maximum height (nearly 6-mm) 
during the fourteenth to twenty-sixth days of menstrual cycle.  At this time, the endometrial 
glands are well developed and secrete a fluid that nourishes the embryo.  Therefore, this 
period is referred to as the secretory phase.  There are abundant blood vessels present in 
the superficial layer of endometrium at this stage.  These are elongated and follow a spiral 
course as they extend from the basal portion to the surface epithelium.  If no pregnancy 
occurs, drop in estrogen and progesterone levels makes the terminal portions of these 
vessels constrict.  This deprives the superficial layers of the uterine lining of a supply of 
oxygen (ischemia) and results in their degeneration.  About two days after the 
vasoconstriction takes place, the affected parts of the uterine lining begin to shed resulting 
in bleeding called the menstrual flow.  This constitutes the menstruation phase.  The 
menstrual fluid consists of epithelium, connective tissue, and blood.  This blood normally 
clots in the uterus and the clots are broken up by enzyme action before flowing from the 
cervix. However, if menstruation at any given time is abnormally rapid, the blood may clot 
in the vagina.  The normal blood loss during a menstrual period is variable, with an average 
of about 50 ml.  Menstruation normally takes four days, with an average of three to six 
days.  At this stage, the endometrium is only about 1 mm thick (Figure 10).  It goes in to a 
three-day repair phase during which i) continuity of the epithelium is re-established, ii) the 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
31 
remaining blood vessels start to grow upward again, and iii) development of glands is 
initiated as invaginations of epithelium.  Rapid growth of the epithelium, blood vessels, and 
connective tissue takes place during the next week.  This is called the proliferative phase.  
It is followed by another secretory phase.  All these changes are closely timed with those 
occurring in the maturing follicle of the ovary. 
 
 
 
 
 
 
 
 
 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
32 
 
Page 4


Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
30 
Fig. 17: Vasculature of Human uterine endometrium. 
Source: ILLL in house 
Cyclic Changes in the Endometrium   
Both the structure and function of the endometrium, including the epithelium, lamina 
propria, glands and blood vessels are subjected to the influence of ovarian steroid hormones 
(Figure 18). Generally, three stages of cellular reorganization are observed during each 
menstrual cycle.  
These are 1) a proliferative phase, 2) a secretory phase, and 3) a menstruation 
phase. During the estrous cycle the uteri also undergo progressive enlargement and 
become distended owing to the accumulation of luminal fluid (next chapter).  
The endometrium of the uterus undergoes pronounced cyclical changes every month during 
a woman’s reproductive years (Figure 18). These changes consist of a gradual building of 
tissue in preparation for receiving a fertilized egg followed by abrupt breakdown of this layer 
and a menstrual flow if pregnancy does not occur.  The endometrial and superficial 
connective tissue layers of the uterine lining are at their maximum height (nearly 6-mm) 
during the fourteenth to twenty-sixth days of menstrual cycle.  At this time, the endometrial 
glands are well developed and secrete a fluid that nourishes the embryo.  Therefore, this 
period is referred to as the secretory phase.  There are abundant blood vessels present in 
the superficial layer of endometrium at this stage.  These are elongated and follow a spiral 
course as they extend from the basal portion to the surface epithelium.  If no pregnancy 
occurs, drop in estrogen and progesterone levels makes the terminal portions of these 
vessels constrict.  This deprives the superficial layers of the uterine lining of a supply of 
oxygen (ischemia) and results in their degeneration.  About two days after the 
vasoconstriction takes place, the affected parts of the uterine lining begin to shed resulting 
in bleeding called the menstrual flow.  This constitutes the menstruation phase.  The 
menstrual fluid consists of epithelium, connective tissue, and blood.  This blood normally 
clots in the uterus and the clots are broken up by enzyme action before flowing from the 
cervix. However, if menstruation at any given time is abnormally rapid, the blood may clot 
in the vagina.  The normal blood loss during a menstrual period is variable, with an average 
of about 50 ml.  Menstruation normally takes four days, with an average of three to six 
days.  At this stage, the endometrium is only about 1 mm thick (Figure 10).  It goes in to a 
three-day repair phase during which i) continuity of the epithelium is re-established, ii) the 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
31 
remaining blood vessels start to grow upward again, and iii) development of glands is 
initiated as invaginations of epithelium.  Rapid growth of the epithelium, blood vessels, and 
connective tissue takes place during the next week.  This is called the proliferative phase.  
It is followed by another secretory phase.  All these changes are closely timed with those 
occurring in the maturing follicle of the ovary. 
 
 
 
 
 
 
 
 
 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
32 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
33 
 
Fig.18: Changes in uterine endometrium during menstrual cycle of 
women. 
Source: 
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/FemaleRepro/femalerepro.htm#Uterus © 
Lutz Slomianka 
Free for educational purpose 
 
 
 
Page 5


Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
30 
Fig. 17: Vasculature of Human uterine endometrium. 
Source: ILLL in house 
Cyclic Changes in the Endometrium   
Both the structure and function of the endometrium, including the epithelium, lamina 
propria, glands and blood vessels are subjected to the influence of ovarian steroid hormones 
(Figure 18). Generally, three stages of cellular reorganization are observed during each 
menstrual cycle.  
These are 1) a proliferative phase, 2) a secretory phase, and 3) a menstruation 
phase. During the estrous cycle the uteri also undergo progressive enlargement and 
become distended owing to the accumulation of luminal fluid (next chapter).  
The endometrium of the uterus undergoes pronounced cyclical changes every month during 
a woman’s reproductive years (Figure 18). These changes consist of a gradual building of 
tissue in preparation for receiving a fertilized egg followed by abrupt breakdown of this layer 
and a menstrual flow if pregnancy does not occur.  The endometrial and superficial 
connective tissue layers of the uterine lining are at their maximum height (nearly 6-mm) 
during the fourteenth to twenty-sixth days of menstrual cycle.  At this time, the endometrial 
glands are well developed and secrete a fluid that nourishes the embryo.  Therefore, this 
period is referred to as the secretory phase.  There are abundant blood vessels present in 
the superficial layer of endometrium at this stage.  These are elongated and follow a spiral 
course as they extend from the basal portion to the surface epithelium.  If no pregnancy 
occurs, drop in estrogen and progesterone levels makes the terminal portions of these 
vessels constrict.  This deprives the superficial layers of the uterine lining of a supply of 
oxygen (ischemia) and results in their degeneration.  About two days after the 
vasoconstriction takes place, the affected parts of the uterine lining begin to shed resulting 
in bleeding called the menstrual flow.  This constitutes the menstruation phase.  The 
menstrual fluid consists of epithelium, connective tissue, and blood.  This blood normally 
clots in the uterus and the clots are broken up by enzyme action before flowing from the 
cervix. However, if menstruation at any given time is abnormally rapid, the blood may clot 
in the vagina.  The normal blood loss during a menstrual period is variable, with an average 
of about 50 ml.  Menstruation normally takes four days, with an average of three to six 
days.  At this stage, the endometrium is only about 1 mm thick (Figure 10).  It goes in to a 
three-day repair phase during which i) continuity of the epithelium is re-established, ii) the 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
31 
remaining blood vessels start to grow upward again, and iii) development of glands is 
initiated as invaginations of epithelium.  Rapid growth of the epithelium, blood vessels, and 
connective tissue takes place during the next week.  This is called the proliferative phase.  
It is followed by another secretory phase.  All these changes are closely timed with those 
occurring in the maturing follicle of the ovary. 
 
 
 
 
 
 
 
 
 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
32 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
33 
 
Fig.18: Changes in uterine endometrium during menstrual cycle of 
women. 
Source: 
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/FemaleRepro/femalerepro.htm#Uterus © 
Lutz Slomianka 
Free for educational purpose 
 
 
 
Female Reproductive System: Structure of Organs and Duct System 
 
              Institute of Life Long Learning, University of Delhi  
 
34 
Many other tissues of the reproductive tract of the female also undergo changes during the 
menstrual cycle, but to a much less extent.  These changes are i) in motility of cilia of the 
oviduct (it is maximal at ovulation), ii) in the viscosity of the cervical mucus, and iii) in the 
cells of vaginal epithelium (next chapter). 
In general, the secretions that line the uterine mucosa during the progestational (secretary) 
phase are rich in carbohydrates, mucopolysaccharide, and proteins.  Ionic composition of 
the uterus also undergoes marked alteration during the preimplantation stages of 
pregnancy.  Also, in species in which capacitation of spermatozoa is a prerequisite for 
fertilization, the uterine secretions may be involved in an alteration of the plasma 
membrane overlying the spermatozoa acrosome, and change it to the fertilizable state.  
Unlike the oviduct, the uterus contains a reduced population of ciliated cells.  Although the 
function of the ciliated cells of the uterus is not as apparent as that of the oviduct, it seems 
likely that these elements participate in the release and distribution of secretory material 
throughout the mucosa.