BSC NURSING SEM1 APPLIED PHYSIOLOGY UNIT 10 The Reproductive System
Female reproductive system-
Female Reproductive System: Anatomy Overview
The female reproductive system consists of external and internal structures. These structures work together for processes such as oogenesis (egg production), fertilization, pregnancy, and childbirth.
External Structures:
Mons Pubis:
Fatty tissue covering the pubic bone.
Protects the underlying bones and organs.
Labia Majora:
Outer folds of skin containing sweat and sebaceous glands.
Protects the internal genital organs.
Labia Minora:
Inner folds of skin without hair.
Protects the vaginal and urethral openings.
Clitoris:
A small, sensitive organ located at the anterior junction of the labia minora.
Plays a role in sexual arousal.
Vestibule:
The area between the labia minora, containing the vaginal and urethral openings.
Bartholin’s Glands:
Located near the vaginal opening.
Secrete mucus to lubricate the vagina.
Internal Structures:
Ovaries:
Almond-shaped organs located on either side of the uterus.
Functions:
Produce eggs (ova).
Secrete hormones: estrogen, progesterone, and inhibin.
Fallopian Tubes (Uterine Tubes):
Tubes that connect the ovaries to the uterus.
Divided into four parts:
Infundibulum: Funnel-shaped end with fimbriae to capture the egg.
Ampulla: The site of fertilization.
Isthmus: Narrow portion connecting to the uterus.
Intramural Part: Embedded in the uterine wall.
Uterus:
A hollow, pear-shaped organ located in the pelvis.
Divided into:
Fundus: Upper, rounded part.
Body: Central portion where implantation occurs.
Cervix: Lower, narrow part connecting to the vagina.
Layers of the uterus:
Perimetrium: Outer layer.
Myometrium: Muscular middle layer.
Endometrium: Inner layer, which thickens during the menstrual cycle.
Vagina:
A muscular canal extending from the cervix to the external body.
Functions:
Passage for menstrual flow.
Birth canal during delivery.
Receptacle for sperm during intercourse.
Cervix:
The lower part of the uterus that opens into the vagina.
Produces cervical mucus to facilitate or inhibit sperm entry, depending on the menstrual cycle phase.
Ligaments Supporting the Reproductive Organs:
Broad Ligament: Supports the uterus, ovaries, and fallopian tubes.
Round Ligament: Maintains the anteverted position of the uterus.
Uterosacral Ligament: Supports the uterus posteriorly.
Ovarian Ligament: Connects the ovary to the uterus.
Blood Supply and Nerve Innervation
Arteries:
Ovarian artery.
Uterine artery.
Vaginal artery.
Nerves:
Autonomic innervation via the pelvic plexus.
Menstrual cycle
Menstrual Cycle: Overview
The menstrual cycle is a natural physiological process that prepares a woman’s body for pregnancy. It is regulated by the interaction of hormones and occurs in a cyclic pattern. The average cycle lasts 28 days, but it can range from 21 to 35 days. The cycle is divided into four main phases:
Phases of the Menstrual Cycle
Menstrual Phase (Day 1–5):
What happens: Shedding of the endometrium occurs, resulting in bleeding (menstruation).
Hormonal changes: Progesterone and estrogen levels drop.
Key event: Endometrial lining is expelled through the vagina.
Follicular Phase (Day 1–13):
What happens: Follicles in the ovaries develop under the influence of Follicle-Stimulating Hormone (FSH).
Hormonal changes: Estrogen levels rise, causing the endometrial lining to thicken.
Key event: One follicle becomes dominant and prepares for ovulation.
Ovulation Phase (Day 14):
What happens: A mature egg (ovum) is released from the ovary due to a surge in Luteinizing Hormone (LH).
Hormonal changes: LH peak triggers ovulation.
Key event: Egg is released and moves into the fallopian tube.
Luteal Phase (Day 15–28):
What happens: The ruptured follicle forms the corpus luteum, which secretes progesterone.
Hormonal changes: Progesterone maintains the endometrial lining for potential implantation.
Key event: If fertilization does not occur, the corpus luteum degenerates, hormone levels drop, and the cycle restarts.
Key Hormones in the Menstrual Cycle
Estrogen:
Stimulates endometrial thickening during the follicular phase.
Progesterone:
Maintains the endometrial lining during the luteal phase.
FSH:
Promotes follicular growth in the ovaries.
LH:
Triggers ovulation.
Clinical Relevance
Irregular Menstrual Cycles: May indicate hormonal imbalances, stress, or underlying health issues.
Dysmenorrhea: Painful menstruation caused by uterine contractions.
Amenorrhea: Absence of menstruation due to pregnancy, hormonal issues, or lifestyle factors.
function and hormones of ovary,
The ovary is a crucial reproductive organ in females, responsible for the production of ova (eggs) and the secretion of hormones. Here is a detailed overview of the functions and hormones of the ovary:
Functions of the Ovary
Oogenesis:
The ovary is responsible for the production and maturation of oocytes (female gametes or eggs) through a process called oogenesis.
This process begins during fetal development and continues in a cyclical manner after puberty until menopause.
Hormone Production:
The ovary synthesizes and secretes essential sex hormones that regulate reproductive cycles, pregnancy, and secondary sexual characteristics.
Regulation of Menstrual Cycle:
The ovary plays a pivotal role in the menstrual cycle by releasing an ovum (ovulation) and preparing the uterus for potential implantation.
Hormones Secreted by the Ovary
The ovary produces three main types of hormones: estrogens, progesterone, and small amounts of androgens.
1. Estrogens
Types: Estradiol (most potent), estrone, and estriol.
Produced by: Follicular cells (granulosa cells) of the developing follicles.
Functions:
Development of female secondary sexual characteristics (e.g., breast development, distribution of body fat).
Regulation of the menstrual cycle (proliferative phase of the endometrium).
Maintenance of bone density and cardiovascular health.
Support of follicular development.
2. Progesterone
Produced by: Corpus luteum (formed after ovulation) and placenta during pregnancy.
Functions:
Prepares the endometrium for implantation of the fertilized egg.
Maintains pregnancy by inhibiting uterine contractions.
Promotes glandular development in the breasts.
3. Androgens
Examples: Testosterone and androstenedione.
Produced by: Theca cells of ovarian follicles.
Functions:
Precursors for estrogen synthesis.
Influence libido and secondary hair growth.
Additional Hormonal Interactions
Inhibin:
Produced by: Granulosa cells of the ovary.
Function: Inhibits follicle-stimulating hormone (FSH) secretion from the anterior pituitary to regulate follicular development.
Activin:
Produced by: Ovarian granulosa cells.
Function: Stimulates FSH secretion and enhances follicular growth.
Relaxin (during pregnancy):
Produced by: Corpus luteum and placenta.
Function: Softens the cervix and relaxes pelvic ligaments during childbirth.
Summary of Hormonal Phases
Follicular Phase (Estrogen dominance):
Growth of ovarian follicles stimulated by FSH.
Estradiol levels peak, leading to ovulation.
Luteal Phase (Progesterone dominance):
Formation of the corpus luteum.
Secretion of progesterone for endometrial preparation.
Ovulation:
Triggered by a surge in luteinizing hormone (LH).
Menstrual Phase:
Occurs if fertilization does not happen, leading to shedding of the endometrial lining.
oogenesis,
Oogenesis: Overview
Oogenesis is the process of formation, growth, and maturation of the female gamete (ovum) within the ovary. It begins during fetal development, pauses at certain stages, and resumes during puberty, continuing until menopause.
Stages of Oogenesis
Oogenesis involves three major stages:
Multiplication phase (Fetal stage)
Growth phase (Puberty onwards)
Maturation phase (During menstrual cycles)
Process of Oogenesis
1. Fetal Stage: Formation of Oogonia
Primordial germ cells migrate to the developing ovaries during early embryogenesis.
These cells differentiate into oogonia through mitotic divisions.
Oogonia multiply rapidly during the fetal period.
By the 5th month of fetal life, all oogonia transform into primary oocytes through the process of differentiation.
2. Arrest in Prophase I (Dictyotene stage)
The primary oocytes enter the first meiotic division but pause at prophase I (specifically in the dictyotene stage) until puberty.
Each primary oocyte is surrounded by a single layer of follicular cells, forming a primordial follicle.
3. Puberty and Follicular Development
At puberty, under the influence of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), some primordial follicles start maturing during each menstrual cycle.
Out of these, usually, one follicle becomes dominant and develops into a Graafian follicle.
4. Completion of Meiosis I
Just before ovulation, the primary oocyte in the dominant follicle completes its first meiotic division.
This division is asymmetric, resulting in:
A secondary oocyte (large cell with most cytoplasm).
A first polar body (small cell, which usually degenerates).
5. Arrest in Metaphase II
The secondary oocyte begins the second meiotic division but halts at metaphase II.
This is the stage at which the oocyte is ovulated and released into the fallopian tube.
6. Completion of Meiosis II (Only after fertilization)
If fertilization occurs, the secondary oocyte completes meiosis II.
This results in:
A mature ovum (haploid, with 23 chromosomes).
A second polar body (small, degenerates).
The haploid nucleus of the ovum fuses with the haploid nucleus of the sperm, forming a zygote.
Key Features
Asymmetric Divisions:
Unequal cytokinesis ensures that the ovum retains most of the cytoplasm, vital for early embryonic development.
Finite Oocyte Reserve:
Females are born with a fixed number of oocytes (~1–2 million at birth).
This number declines to ~300,000 by puberty, with only ~400–500 oocytes ovulated during a woman’s reproductive life.
Regulation by Hormones:
FSH stimulates follicular growth.
LH surge triggers ovulation and completion of meiosis I.
Phases of Follicular Development in Oogenesis
Primordial Follicle:
Contains a primary oocyte arrested in prophase I.
Primary Follicle:
Surrounded by a single layer of cuboidal granulosa cells.
Secondary Follicle:
Contains multiple layers of granulosa cells and theca cells.
Tertiary Follicle (Graafian Follicle):
Mature follicle with a fluid-filled antrum.
Houses the secondary oocyte, ready for ovulation.
Comparison of Oogenesis and Spermatogenesis
Feature
Oogenesis
Spermatogenesis
Start
Fetal stage
Puberty
Gamete Produced
1 ovum per oogonium
4 spermatozoa per spermatogonium
Arrest Phases
Prophase I, Metaphase II
None
Completion
Fertilization
Continuous after puberty
fertilization
Fertilization: Overview
Fertilization is the process in which a male gamete (sperm) fuses with a female gamete (ovum) to form a zygote, marking the beginning of a new organism’s life. It typically occurs in the ampulla of the fallopian tube, which is the widest part of the tube.
Steps of Fertilization
Capacitation of Sperm:
Sperm undergo biochemical changes in the female reproductive tract to become capable of fertilizing the egg.
Changes include removal of glycoproteins and cholesterol from the sperm membrane, increasing motility and membrane fluidity.
Sperm Penetration of Corona Radiata:
The ovum is surrounded by a layer of follicular cells called the corona radiata.
Sperm use their flagellar movement and enzymes (e.g., hyaluronidase) to penetrate this layer.
Binding to Zona Pellucida:
The sperm binds to a glycoprotein in the zona pellucida (a protective glycoprotein layer surrounding the oocyte).
The binding is mediated by specific receptors on the sperm head.
Acrosome Reaction:
Enzymes from the sperm’s acrosome (a cap-like structure) are released.
These enzymes, such as acrosin, help digest the zona pellucida, allowing the sperm to reach the oocyte membrane.
Fusion of Sperm and Oocyte Membranes:
The sperm membrane fuses with the oocyte’s plasma membrane.
The sperm head and tail enter the cytoplasm of the oocyte, leaving the sperm’s membrane behind.
Cortical Reaction:
The fusion triggers the release of calcium ions in the oocyte.
This causes the release of enzymes from cortical granules, which modify the zona pellucida, making it impermeable to other sperm (block to polyspermy).
Completion of Meiosis II:
The secondary oocyte, which was arrested in metaphase II, completes its second meiotic division.
This forms a haploid ovum and a second polar body.
Formation of the Male and Female Pronuclei:
The sperm nucleus decondenses to form the male pronucleus.
The haploid nucleus of the ovum becomes the female pronucleus.
Fusion of Pronuclei:
The male and female pronuclei fuse to form a single diploid nucleus.
The resulting cell, called a zygote, has 46 chromosomes (23 pairs).
Initiation of Cleavage:
The zygote undergoes mitotic divisions, forming a multicellular structure as it travels toward the uterus for implantation.
Key Features of Fertilization
Site:
Occurs in the ampulla of the fallopian tube.
Time Frame:
Fertilization typically happens within 24 hours after ovulation.
The oocyte remains viable for 12–24 hours, while sperm can survive in the female reproductive tract for up to 5 days.
Restoration of Diploid Number:
Fertilization restores the diploid chromosome number (46 chromosomes).
Sex Determination:
The sperm determines the sex of the offspring:
X-bearing sperm results in a female (XX).
Y-bearing sperm results in a male (XY).
Activation of the Zygote:
Fertilization activates the oocyte, initiating metabolic processes required for cleavage and development.
Clinical Relevance
Polyspermy:
Rare condition where more than one sperm fertilizes the egg, leading to an abnormal zygote that is not viable.
Assisted Reproductive Technology (ART):
Techniques like in vitro fertilization (IVF) replicate the fertilization process outside the body.
Ectopic Pregnancy:
Fertilization occurs outside the ampulla, often leading to implantation in abnormal sites like the fallopian tube.
implantation,
Implantation: Overview
Implantation is the process by which the blastocyst (a structure formed in early embryonic development) attaches to and embeds itself into the endometrium (the inner lining of the uterus). This is a critical step for establishing pregnancy.
Stages of Implantation
The implantation process occurs in three key stages:
Apposition:
The blastocyst loosely attaches to the endometrium.
This typically occurs at a site where the endometrium is most receptive, usually in the posterior or upper uterine wall.
Adhesion:
The blastocyst firmly adheres to the endometrial lining.
The outer layer of the blastocyst, called the trophoblast, starts to proliferate and differentiate.
Invasion:
The trophoblast invades the endometrial tissue to secure the blastocyst.
It penetrates deeper into the endometrium, forming connections with maternal blood vessels for nutrient and oxygen exchange.
Process of Implantation
Preparation of the Endometrium:
The endometrium becomes receptive under the influence of estrogen and progesterone (secreted by the corpus luteum).
The decidual reaction occurs:
Endometrial stromal cells enlarge and become rich in glycogen and lipids to nourish the embryo.
Formation of the Blastocyst:
The zygote undergoes mitotic divisions (cleavage), forming a morula.
The morula develops into a blastocyst, consisting of:
Trophoblast (outer layer): Forms the placenta.
Inner cell mass (ICM): Develops into the embryo.
Attachment:
Around 6-7 days post-fertilization, the blastocyst reaches the uterus.
It orients itself so that the embryonic pole (the side with the ICM) contacts the endometrium.
Trophoblast Differentiation:
The trophoblast differentiates into two layers:
Cytotrophoblast: Inner layer of trophoblast cells.
Syncytiotrophoblast: Outer multinucleated layer that invades the endometrium.
Invasion:
The syncytiotrophoblast secretes enzymes that erode the endometrial tissue, allowing the blastocyst to embed itself.
The maternal blood vessels are breached, forming spaces (lacunae) that later develop into the placental circulation.
Establishment of Maternal-Fetal Circulation:
By the end of the second week, the implanted blastocyst establishes connections with the maternal blood supply through the developing chorionic villi.
Timeline of Implantation
Day 0: Fertilization occurs in the ampulla of the fallopian tube.
Days 3-4: Morula reaches the uterus.
Days 5-6: Blastocyst forms and begins hatching from the zona pellucida.
Days 6-7: Blastocyst attaches to the endometrium.
Days 8-10: Blastocyst invades the endometrium and becomes fully embedded.
Hormonal Support of Implantation
Progesterone:
Secreted by the corpus luteum.
Prepares and maintains the endometrium for implantation.
Human Chorionic Gonadotropin (hCG):
Secreted by the syncytiotrophoblast after implantation.
Maintains the corpus luteum, ensuring continued secretion of progesterone.
Estrogen:
Promotes growth and vascularization of the endometrium.
Types of Implantation
Superficial Implantation:
Blastocyst attaches to the surface of the endometrium (e.g., humans).
Interstitial Implantation:
Blastocyst penetrates deeply into the endometrium (e.g., humans).
Central Implantation:
Blastocyst remains in the central uterine cavity, not deeply embedded (e.g., some animals).
Clinical Significance
Ectopic Pregnancy:
Occurs when the blastocyst implants outside the uterus, commonly in the fallopian tube.
This is a medical emergency requiring prompt intervention.
Implantation Failure:
Can lead to infertility or early pregnancy loss.
Causes include uterine abnormalities, hormonal imbalances, or genetic defects in the embryo.
Assisted Reproductive Technology (ART):
In procedures like in vitro fertilization (IVF), embryos are transferred to the uterus to aid implantation.
Functions of breast
Functions of the Breast
The breasts are specialized structures in the human body, primarily involved in the production and delivery of milk for infant nourishment. Additionally, they play roles in hormonal regulation, sexual health, and immune functions.
Primary Functions
1. Lactation (Milk Production and Secretion):
The primary biological function of the breast is to produce and secrete milk to nourish newborns.
Key processes involved:
Milk Production: Occurs in the alveoli of mammary glands, stimulated by the hormone prolactin.
Milk Ejection: Facilitated by the contraction of myoepithelial cells under the influence of oxytocin during breastfeeding.
2. Nutrition for the Newborn:
Breast milk provides all essential nutrients, antibodies, and growth factors required for an infant’s development.
It contains:
Macronutrients: Proteins (casein, whey), fats, and carbohydrates (lactose).
Micronutrients: Vitamins and minerals.
Immunological Factors: Antibodies (e.g., IgA), lactoferrin, and lysozymes.
Secondary Functions
1. Immune Protection for the Infant:
Breast milk contains immunoglobulins (primarily IgA) that protect the infant against infections.
It provides passive immunity and reduces the risk of diseases like diarrhea, respiratory infections, and otitis media.
2. Hormonal and Emotional Bonding:
Oxytocin release during breastfeeding promotes mother-infant bonding.
It fosters emotional attachment and reduces maternal stress.
3. Role in Reproductive Health:
Breastfeeding suppresses ovulation temporarily by inhibiting the release of gonadotropin-releasing hormone (GnRH), acting as a natural contraceptive (lactational amenorrhea).
Additional Functions
1. Sexual Function:
The breasts have erogenous zones and play a role in sexual arousal and intimacy.
2. Endocrine Role:
The breast tissue is responsive to hormonal changes (e.g., estrogen, progesterone, prolactin), which regulate its development and function.
3. Psychological Role:
The breasts contribute to body image, self-esteem, and cultural perceptions of femininity.
Developmental Stages and Functions
The function of the breast changes throughout different life stages:
Puberty:
Estrogen and progesterone stimulate the development of breast tissue and ductal systems.
Pregnancy:
Breasts enlarge due to hormonal changes (increased levels of estrogen, progesterone, prolactin, and hCG).
Alveoli and duct systems prepare for milk production.
Lactation:
Following childbirth, prolactin and oxytocin coordinate milk production and ejection.
Post-Lactation:
Breast tissue undergoes involution after lactation ceases.
Menopause:
Decline in estrogen levels leads to atrophy of glandular tissue and an increase in fatty deposits.
Clinical Relevance
Breastfeeding Benefits:
Reduces the risk of breast cancer and ovarian cancer in mothers.
Promotes healthy growth and immunity in infants.
Breast Disorders:
Mastitis: Infection during breastfeeding.
Fibrocystic Changes: Benign breast lumps.
Breast Cancer: A malignant disease that requires early detection and treatment.
Surgical Importance:
Breasts are considered during reconstructive surgeries, mastectomies, or cosmetic enhancements.
Male reproductive system- Spermatogenesis
Male Reproductive System: Spermatogenesis
Spermatogenesis is the process of the production and maturation of spermatozoa (sperm cells) in the male testes. It occurs in the seminiferous tubules, begins at puberty, and continues throughout life.
Overview of Spermatogenesis
Site: Seminiferous tubules of the testes.
Duration: Approximately 64–72 days for a complete cycle.
Outcome: Formation of haploid spermatozoa from diploid spermatogonia.
Stages of Spermatogenesis
Spermatogenesis occurs in three phases:
Multiplication (Mitotic Division) Phase
Meiotic Phase
Spermiogenesis (Differentiation Phase)
1. Multiplication Phase (Mitotic Division)
Spermatogonia (diploid, 2n) are the stem cells of the testes.
These cells undergo mitotic division to produce more spermatogonia.
Some spermatogonia differentiate into primary spermatocytes, which enter meiosis.
2. Meiotic Phase
This phase involves two meiotic divisions:
First Meiotic Division:
Each primary spermatocyte (2n) undergoes meiosis I.
This produces two secondary spermatocytes (haploid, n).
Second Meiotic Division:
Each secondary spermatocyte undergoes meiosis II.
This results in four spermatids (haploid, n).
3. Spermiogenesis (Differentiation Phase)
Spermatids transform into mature spermatozoa (sperm cells) through a series of morphological changes:
Development of a flagellum for motility.
Condensation of the nucleus for genetic material compaction.
Formation of the acrosome (enzyme-filled cap) to penetrate the egg.
Shedding of excess cytoplasm.
The mature spermatozoa are then released into the lumen of the seminiferous tubules.
Structure of a Mature Sperm
Head:
Contains the nucleus with haploid chromosomes.
Acrosome (cap-like structure) contains enzymes (e.g., hyaluronidase) to penetrate the ovum.
Midpiece:
Packed with mitochondria to provide energy for motility.
Tail (Flagellum):
Facilitates movement toward the ovum.
Hormonal Regulation of Spermatogenesis
Hypothalamic-Pituitary-Gonadal Axis:
The hypothalamus secretes GnRH (Gonadotropin-Releasing Hormone).
GnRH stimulates the anterior pituitary to release:
FSH (Follicle-Stimulating Hormone): Stimulates Sertoli cells to support spermatogenesis.
LH (Luteinizing Hormone): Stimulates Leydig cells to produce testosterone.
Testosterone:
Secreted by Leydig cells.
Essential for the initiation and maintenance of spermatogenesis.
Inhibin:
Produced by Sertoli cells.
Inhibits FSH secretion to regulate spermatogenesis.
Factors Affecting Spermatogenesis
Temperature:
Spermatogenesis requires a temperature slightly lower than body temperature (~34°C).
The scrotum maintains this optimal temperature.
Hormonal Imbalances:
Low levels of FSH, LH, or testosterone can impair spermatogenesis.
Nutrition:
Deficiencies in vitamins (e.g., vitamin A, zinc) can reduce sperm production.
Lifestyle:
Smoking, alcohol, stress, and exposure to toxins can adversely affect sperm production.
Clinical Relevance
Infertility:
Low sperm count (oligospermia), abnormal sperm morphology, or poor motility can lead to infertility.
Cryptorchidism:
Undescended testes impair spermatogenesis due to high abdominal temperature.
Hormonal Disorders:
Hypogonadism or pituitary dysfunction can disrupt spermatogenesis.
Assisted Reproductive Technology (ART):
Techniques like in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) help overcome spermatogenesis-related infertility.
hormones and its functions,
Hormones and Their Functions
Hormones are chemical messengers secreted by endocrine glands that regulate various physiological processes in the body. They are transported through the bloodstream to target organs or tissues, where they exert specific effects.
Types of Hormones Based on Structure
Peptide/Protein Hormones:
Composed of amino acids.
Example: Insulin, Glucagon.
Steroid Hormones:
Derived from cholesterol.
Example: Estrogen, Testosterone.
Amine Hormones:
Derived from amino acids like tyrosine.
Example: Thyroxine, Epinephrine.
Major Hormones and Their Functions
1. Hypothalamic Hormones
Gonadotropin-Releasing Hormone (GnRH):
Stimulates the release of FSH and LH from the anterior pituitary.
Thyrotropin-Releasing Hormone (TRH):
Stimulates the release of TSH and prolactin.
Corticotropin-Releasing Hormone (CRH):
Stimulates the release of ACTH.
Growth Hormone-Releasing Hormone (GHRH):
Stimulates the release of GH.
2. Pituitary Hormones
Anterior Pituitary:
Growth Hormone (GH):
Promotes growth of bones, muscles, and tissues.
Regulates metabolism.
Prolactin:
Stimulates milk production in lactating mothers.
Adrenocorticotropic Hormone (ACTH):
Stimulates adrenal glands to produce cortisol.
Thyroid-Stimulating Hormone (TSH):
Stimulates the thyroid gland to release T3 and T4.
Follicle-Stimulating Hormone (FSH):
Stimulates ovarian follicle development in females and spermatogenesis in males.
Luteinizing Hormone (LH):
Triggers ovulation in females and testosterone production in males.
Posterior Pituitary:
Oxytocin:
Stimulates uterine contractions during childbirth and milk ejection during breastfeeding.
Antidiuretic Hormone (ADH/Vasopressin):
Regulates water balance by increasing water reabsorption in the kidneys.
3. Thyroid Hormones
Thyroxine (T4) and Triiodothyronine (T3):
Regulate metabolism, growth, and development.
Calcitonin:
Lowers blood calcium levels by inhibiting bone resorption.
4. Parathyroid Hormone (PTH)
Parathyroid Hormone (PTH):
Increases blood calcium levels by stimulating bone resorption and calcium reabsorption in kidneys.
5. Adrenal Gland Hormones
Adrenal Cortex:
Cortisol:
Regulates metabolism, immune response, and stress response.
Aldosterone:
Regulates sodium and potassium balance and blood pressure.
Androgens:
Precursor to sex hormones.
Adrenal Medulla:
Epinephrine (Adrenaline) and Norepinephrine (Noradrenaline):
Mediate the fight-or-flight response, increasing heart rate, blood pressure, and energy supply.
6. Pancreatic Hormones
Insulin:
Lowers blood glucose levels by facilitating cellular glucose uptake.
Glucagon:
Raises blood glucose levels by promoting glycogen breakdown in the liver.
Somatostatin:
Inhibits the release of insulin, glucagon, and growth hormone.
7. Reproductive Hormones
Ovaries:
Estrogen:
Develops and maintains female secondary sexual characteristics and regulates the menstrual cycle.
Progesterone:
Prepares the uterus for implantation and maintains pregnancy.
Testes:
Testosterone:
Develops and maintains male secondary sexual characteristics and supports spermatogenesis.
8. Pineal Hormone
Melatonin:
Regulates sleep-wake cycles and biological rhythms.
9. Gastrointestinal Hormones
Gastrin:
Stimulates gastric acid secretion.
Secretin:
Stimulates the release of bicarbonate from the pancreas.
Cholecystokinin (CCK):
Stimulates bile release from the gallbladder and pancreatic enzyme secretion.
10. Other Important Hormones
Erythropoietin (EPO) (Kidneys):
Stimulates red blood cell production in the bone marrow.
Leptin (Adipose Tissue):
Regulates appetite and energy balance.
Renin (Kidneys):
Plays a role in blood pressure regulation through the renin-angiotensin-aldosterone system.
Summary Table
Hormone
Source
Function
Growth Hormone (GH)
Anterior Pituitary
Promotes growth and metabolism.
Thyroxine (T4), Triiodothyronine (T3)
Thyroid Gland
Regulates metabolism.
Cortisol
Adrenal Cortex
Manages stress, metabolism.
Insulin
Pancreas
Lowers blood glucose.
Testosterone
Testes
Male reproductive functions.
Estrogen
Ovaries
Female reproductive functions.
Oxytocin
Posterior Pituitary
Uterine contractions, milk ejection.
ADH (Vasopressin)
Posterior Pituitary
Regulates water balance.
semen
Semen: Overview
Semen, also known as seminal fluid, is a viscous, whitish fluid that is ejaculated from the male reproductive system during ejaculation. It serves as a medium to transport sperm and provides a supportive environment for the survival and motility of sperm cells.
Composition of Semen
Semen is composed of secretions from various glands in the male reproductive system:
Spermatozoa (Sperm Cells):
Produced in the testes.
Comprises about 1–5% of the total semen volume.
Function: Fertilization of the female egg.
Seminal Plasma:
Accounts for ~95–99% of semen and is composed of fluids from:
Seminal Vesicles (~60–70%):
Secretes a fructose-rich fluid to provide energy for sperm motility.
Contains prostaglandins, which aid in uterine contractions and sperm transport.
Prostate Gland (~25–30%):
Produces a milky, alkaline fluid to neutralize the acidic environment of the vagina.
Contains enzymes like prostate-specific antigen (PSA), which liquefy semen after ejaculation.
Bulbourethral Glands (Cowper’s Glands) (~5%):
Produces a mucus-like fluid that lubricates the urethra and neutralizes residual acidity from urine.
Characteristics of Semen
Volume:
Average ejaculate volume: 2–5 mL.
Sperm Concentration:
Normal: 15–200 million sperm/mL.
Low sperm count (<15 million/mL) may indicate infertility (oligospermia).
pH:
Slightly alkaline (pH 7.2–7.8) to neutralize the acidic vaginal environment.
Consistency:
Initially thick and coagulated but becomes liquefied within 15–30 minutes after ejaculation due to enzymes like PSA.
Color:
Milky white to slightly yellowish.
Functions of Semen
Transport:
Provides a medium for sperm to travel through the male and female reproductive tracts.
Nutrition:
Supplies energy to sperm through fructose and other nutrients.
Protection:
Alkalinity helps protect sperm from the acidic environment of the vagina.
Antioxidants protect sperm from oxidative stress.
Motility:
Prostaglandins enhance sperm motility and assist in movement through the female reproductive tract.
Fertilization:
Facilitates the delivery of sperm to the egg for fertilization.
Clinical Relevance
Semen Analysis:
A diagnostic test used to evaluate male fertility.
Parameters assessed:
Volume
Sperm concentration
Motility
Morphology
Disorders of Semen:
Oligospermia: Low sperm count.
Azoospermia: Absence of sperm in semen.
Asthenospermia: Reduced sperm motility.
Teratospermia: Abnormal sperm morphology.
Use in Assisted Reproductive Technology (ART):
Semen is processed and used in techniques like in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) to treat infertility.