Reproductive Physiology Midterm Exam PDF

PATHWAYS TO PREGNANCY AND PARTURITION Chapter 1 Reproductive Physiology - a field of study that deals primarily with reproduction in food-producing animals. Reproductive Science - a study of reproductive processes, a subspecialty of physiology Subspecialties: 1. Andrology - study in male ani...

PATHWAYS TO PREGNANCY AND PARTURITION Chapter 1 Reproductive Physiology - a field of study that deals primarily with reproduction in food-producing animals. Reproductive Science - a study of reproductive processes, a subspecialty of physiology Subspecialties: 1. Andrology - study in male animals and humans 2. Gynecology - reproductive issues in women 3. Theriogenology - focuses on the reproductive system in animals 4. Obstetrics - specialize in females, before, during, and after parturition. History of Reproductive Physiology: 1. Aristotle (Around 350 BC) - believed that a fetus originates from menstrual blood, has a book “Generation of Animals”. 2. Fallopius (1562) - discovered and described oviducts, the name Fallopian tube reflects his discovery. 3. Coiter (1573) - discovered and described corpus luteum 4. Regnier de Graaf (1672) - described antral follicle that has been named the Graafian follicle. 5. Antonie van Leeuwenhoek (1677) - discovered and described spermatozoa in semen. He refers to it as “animalcules”. 6. Spallanzani (1780) - the father of modern AI, performed the first AI in a dog. - Hypothesized spermatozoa as fertilizing agents 7. Dumas (1825) - proved spermatozoa as fertilizing agents; this marked the beginning of modern reproductive physiology.  Modern reproductive physiology can be described as an “explosion of knowledge” Prostaglandin F2α regulates the length of the estrous cycle in most mammalian females. Chapter 2 The Female Reproductive Tract includes: 1. Ovaries - produce gametes and a variety of hormones 2. Oviducts - provide an environment for fertilization, a site for the pre-attachment development of an embryo. 3. Uterus - environment for sperm transport, site for attachment of conceptus. 4. Cervix - a barrier that secretes mucus during estrus, and produces a cervical seal during pregnancy. 5. Vagina - the copulatory organ that produces lubricating mucus. 6. External genitalia Rectogenital Pouch - separates the reproductive tract from the rectum Series of tubes (layers): 1. Serosa (outer) - single cell layer that covers the surface of the reproductive tract. 2. Muscularis - a double layer of smooth muscle, that provides a tubular component with the ability to contract. MUSCLE. 3. Submucosa - a layer of varying thickness, this region houses blood vessels 4. Mucosa (inner) - secretory layer of epithelium Retroperitoneal Position - how the reproductive tract develops  Peritoneum - connective tissue lining of abdominal cavity, surrounds or covers reproductive tract. Broad ligament - suspensory tissue, double layered connective tissue sheets that support and suspend ovaries, oviduct, uterus, and cervix. - Houses the vascular supply, lymphatic drainage, and nerves. Components of the broad ligament: 1. Mesovarium - anterior (cranial) portion attaches to and supports the ovary. - Houses the blood and lymphatic vessels and nerves that supply ovary, and forms the hilus. 2. Mesosalpinx - thin, serous part, also serves as a bursa-like pouch that surrounds the ovary. This also helps orient the infundibulum. 3. Mesometrium - largest and most conspicuous part. Supports the uterine horns (cornua) and body of the uterus. OVARY - An ovoid, relatively dense, produces female gametes (ova) and hormones estrogen and progesterone. - Composed of an outer connective tissue called the tunica albuginea. Tunica Albuginea - covered by a single layer of cuboidal cells called germinal epithelium. - Germinal epithelium - no function related to production Ovarian Cortex - beneath tunica albuginea, houses a population of oocytes. Also houses the functional corpus luteum.  Corpus luteum - a temporary collection of cells on the ovary each menstrual cycle. - Produces oxytocin, relaxin, inhibin and activin. Corpora lutea - plural, “yellow bodies”, large and conspicuous that produces progesterone. Corpora albicantia - degenerating corpora lutea, corpus albicans - singular - Readily observed, “albicans from the word albino, it represents white” - As CL degenerates, it undergoes a gradual color transition from orange/yellow to white scar-like structure. Ovarian Medulla - the central part of the ovary, houses vasculature, nerves, and lymphatics and is composed of relatively dense connective tissue. Ovulation fossa - where ovulation occurs in the mare. Folliculogenesis - a process whereby immature follicles develop into more advanced follicles and become candidates for ovulation. Four types of follicles are present within the ovary: *Females are born with a lifetime supply of primordial follicles and primary follicles. 1. Primordial follicles - microscopic, the most immature, smallest 2. Primary follicle - does not divide into other primary follicles, they either develop or degenerate. 3. Secondary follicles - two or more layers of follicle cells, but without antrum or cavity. Surrounded by a thick translucent layer called “zona pellucida”. 4. Antral follicle - also referred to as “tertiary follicle” when it becomes dominant it is sometimes called “graafian follicle” - fluid-filled cavity called an “antrum” - The fluid in the antrum is called “follicular fluid” - sometimes observed in the naked eye, appear as blisters like.. Three Layers of Antral Follicles: 1. Theca externa - loose connective tissue that completely surrounds and supports the follicle. 2. Theca interna - beneath theca externa, cells are responsible for the production of androgens under the influence of LH. 3. Granulosal Cell Layer - sometimes called “membrana granulosa” - Produce a variety of materials and have FSH receptors - Important products are estrogen, inhibin, and follicular fluid. - Also believed to govern the maturation of oocytes. Corpus hemorrhagicum - also called “bloody body”, ruptured blood vessels OVIDUCT The oviduct consists of: 1. Infundibulum - terminal end of the oviduct, funnel-shaped opening - The surface is covered with many velvety, finger-like “fimbriae” - The oocyte will be “captured” and transported in the “ostium” - Surface area of 6-10 cm2 in sheep, 20-30 cm2 in cattle. 2. Ampulla - thick portion of the oviduct, merges with the isthmus. - Large diameter, many fern-like mucosal folds with ciliated epithelium Ampullary isthmic junction - the junction between the ampulla and isthmus. 3. Isthmus - smaller in diameter than ampulla, has a thicker muscular wall - “Uterotubal junction” - isthmus and uterus junction UTERUS - Is the organ of pregnancy - In most mammals, the uterus consists of two uterine horns or cornua. Types of Uteri found in Mammals: 1. Duplex Uterus (two cervices) - characterized as having two cervical canals that separate each uterine horn into distinct compartments. Two types of duplex uteri: Bifurcates (splits) - Marsupials - In opposums, the female anatomical configuration is accommodated by the forked penis of the male. - It is believed that after intromission, the male deposits semen on each of the two sides simultaneously. Two Uterine Horns - Rabbits 2. Bicornuate Uterus - having two uterine horns and a small uterine body - A single cervical canal - Bipartite was once used to describe bicornuate uteri with short (mare) to moderate (cow) length uterine horns. 3. Simplex - no uterine horns - Primates and humans Components of Uterus: 1. Perimetrium (serosa) - serosal layer that is part of the peritoneum. It is continuous with the serosal layer covering the mesosalpinx. 2. Myometrium (muscularis) - beneath the serosal layer is a longitudinal layer of smooth muscle. The outer longitudinal layer and inner circular muscle layer. - Provides motility ( a form of contraction) for the uterus. During parturition, the myometrium becomes a major driving force for the expulsion of the fetus and fetal membranes. 3. Endometrium (mucosa + submucosa) - inner portion of the uterus.  - Responsible for secreting materials into the lumen of the uterus that enhance embryo development and sperm viability. Primary functions of the uterus are: Sperm transport Luteolysis and control of cyclicity Environment for pre-attachment embryo Maternal contribution to the placenta Expulsion of the fetus and fecal placenta CERVIX - Provides lubrication, a flushing system, and a barrier during pregnancy. - Relatively thick-walled, non-compliant organ that serves as a barrier to sperm transport in the ewe, cow, bitch, and queen but not in the sow and mare. - Isolates the uterus from the external environment during pregnancy by forming a barrier consisting of highly viscous mucus. Cervical seal. - The cervix of the cow and ewe have distinct protrusions called Cervical Rings (CR) - The sow has interdigitating prominences (IP). - The mare has no cervical rings but has many cervical folds (CF). VAGINA - Is the copulatory organ. - Site of expulsion of urine during micturition - A passive birth canal during parturition Chapter 3 Male Reproductive Tract Testes - serve as the manufacturing and assembly plant for spermatozoa. Spermatogenesis - it is a process of forming of sperm. Epididymis - storage of sperm for maturation and to transfer it to vas deferens. -head (caput) and body (corpus) - fertility -Tail (cauda)- warehouse and shipping center. (motility) Seminal Plasma - spermatozoa that is mixed with fluids produced by the accessory glands. Note: Once sperm are mixed with seminal plasma , they are available for delivery by ejaculation. The Delivery system is the penis and specific muscles are responsible for erection, protrusion of the penis and ejaculation of semen. The basic components of the male reproductive system are: Spermatic cord - the passageway from the body cavity into the scrotum.  - provides the pathway to and from the body for the testicular vasculature, lymphatics and neural connection to the body. - spermatic cord also houses the ductus deferens, the cremaster muscle and a specialized vascular network called the pampiniform plexus. - provide heat exchanger Pampiniform plexus - The testicular veins in the spermatic cord branch into an elaborate network that fonns many intimate finger-like "wrappings" surrounding the highly convoluted testicular artery. -it also forms a single vein that runs into the caudal vena cava. Scrotum - It protects and supports the testes and is required for proper temperature regulation. Testis Excurrent duct system Accessory sex glands Penis and muscles for protrusion, erection, and ejaculation. Countercurrent heat exchanger - a thermoregulatory response in favor of spermatogenesis. - Heat from the warm (39°C) arterial blood from the body is transferred to the cooler (33°C) venous blood leaving the surface of the testes.This venous blood has been cooled by direct heat loss from the testicular veins through the skin of the scrotum. Maintenance of low testicular temperature is obligatory for spermatogenesis in domestic animals and man. Long convoluted testicular artery - Serves as a pulse pressure eliminator. Pulse pressure is what you feel when you palpate the radial artery in your wrist or the carotid artery in your neck. It is the differ- ence between systolic pressure (heart contraction) and diastolic pressure (heart relaxation). Cremaster muscle - The primary supporting the testis and coursing the length of the spermatic cord. - It is also a striated muscle that continuous with the internal abdominal oblique muscles. - It helps support the testis and aids in control of testicular temperature. - Contractions of the cremaster muscle promote venous return of testicular blood and thus facilitates heat exchange. Not all animals have pendular testes that are located outside of the body. Birds, elephants, sloths, armadillos and some marine mammals (whales and dolphins) have testes located inside the body in a retroperitoneal position. Thus, mechanisms associated with temperahire regulation are not important in these species, except where loss of control of deep body temperature occurs. Animals that do not have scrotum: Birds, elephants, sloths, armadillos, and some marine mammals (whales and dolphins). The testes of some mammals (rat and rabbit) move into and out of the body cavity throughout their lives through a patent inguinal canal. The evolutionary basis for the descent of the testes and the need for testicular cooling is not clear. Scrotum - Is a thermosensor, swamp cooler, and protective sac The scrotum consists of four major layers. - Skin - Tunica dartos - Scrotal fascia - Parietal vaginal tunic Scrotal Skin - is heavily populated with sweat glands. These sweat glands are required for maintenance of proper testicular temperature. - is endowed with large number of thermosensitive nerves that govern both the degree of scrotal sweating and the respiratory rate of the animal. Infrared thermography - a noninvasive technology that have been used by Canadian researchers to assess the cooling capacity of the testes.  Tunica Dartos- Also known as dartos muscle is a mesh-like smooth muscle layer that lies just beneath the scrotal skin. The degree of contraction of this smooth muscle is constantly adjusted in response to changes in scrotal skin temperature. The sensory nerves initiating the changes in the tone ( degree of contraction) of the tunica dartos are located in the scrotal skin. Unlike striated muscle ( cremaster muscle), the smooth muscle of the tunica dartos can maintain sustained contractions. - Development and maintenance of the contractile ability of the tunica dartos are under androgen control. Artificial manipulation of the scrotum has been used to sterilize beef bulls. A bull subjected to this procedure is referred to as a "short scrotumed" bull. This type of bull is physiologically an artificial cryptorchid. Testes - are the primary reproductive organs in the male. - Production of spermatozoa, hormones(testosterone) and proteins. - Fluid produced by the testes (sometimes called rete fluid) also contains products synthesized by the sertoli cells. Relationship of the Germ cells to the adjacent sertoli cells: Peripheral Adluminal Compartment - During elongation of the spermatid nucleus, the spermatids are repositioned by the Sertoli cells to become imbedded within long pockets in the cytoplasm of an individual Sertoli cell. When released as a spermatozoon, a major portion of the cytoplasm of each  spermatid remains as a residual body (cytoplasmic droplet) within a pocket of the Sertoli cell cytoplasm. Deep Adluminal Compartment - The primary spermatocytes are moved from the basal compartment through the tight junctions between adjacent Sertoli cells into the adluminal compartment where they eventually divide to form secondary spermatocytes (not shown) and spherical spermatids. The spermatogonia, primary spermatocytes, secondary spermatocytes and spherical spermatids all develop in the space between two or more Sertoli cells and are in contact with them. Note the intracellular bridges between adjacent germ cells in the same cohort or generation. Basal Compartment - Formation of spermatozoa in the seminiferous epithelium starts near the basement membrane. Here a spermatogonium divides to form other spermatogonia and, ultimately, primary spermatocytes Testis consist of: A. Testicular capsule B. Parenchyma C. Mediastinum D. Rete tubules A. Testicular capsule - is a covering of the testis.  - Composed of two layers - They are the visceral vaginal tunic and the connective tissue capsule also known as the tunica albuginea. Tunica albuginea sends many fingerlike projections into parenchyma of the testicle. These septal projections join with the mediastinum. Tunica vasculosa is an interior surface of the tunica albuginea and surfaces the septal divisions forming the lobulest that are quite vascular. Testicular parenchyma consists of: Seminiferous tubules Interstitial cells of Leydig Capillaries Lymphatic vessels Connective tissue B. Parenchyma - The word parenchyma refers to specific cellular mass of a gland or organ that is supported by a connective tissue network. The major cellular mass of the testis is therefore referred to as the parenchyma. - It is soft, tan (sometimes brown or gray) mass made up of seminiferous tubules and interstitial tissue (blood vessels, nerves, lymphatics, connective tissue and Leydig cells) - Can be divided into tubular compartment and the interstitial compartment. The tubular compartment is consists of seminiferous tubules and all of the cells and materials inside them. The interstitial compartment is consists of all cells and materials outside the seminiferous tubules, such as blood vessels, connective tissue, lymphatics, nerves and insterstitial cells of Leydig, that produce testosterone. C. Mediastinum - is the central connective tissue core of the testis that houses ducts called rete tubules. Rete tubules - or rete testis are tiny channels through which spermatozoa are transported out of the testis. Tubular compartment consists of: - Seminiferous epithelium - Sertoli cells - Developing germ cells - Peritubular cells Seminal Plasma is a Non-Cellular Fluid Vehicle for Spermatozoal Delivery to the Female Epididymis and accessory sex glands- responsible for production of secretions that contribute to the liquid, noncellular portion of semen known as seminal plasma.  Seminal plasma- is not required for fertility, but is important in natural insemination where a fluid vehicle for delivery of the sperm is needed. Spermatozoa that are removed from the tail of the epididymis are equally as fertile as those that are ejaculated. In fact, when dairy bulls of genetic superiority die, spermatozoa can be flushed from the epididymal tail, processed and frozen. Artificial removal of these reserves can result in the generation of 600 to 1000 additional units of frozen semen. In some species (the boar and stallion), the seminal plasma possesses special coagulation properties that plug the female reproductive tract and minimize loss of spermatozoa following copulation and ejaculation. Accessory sex glands secrete their products into the lumen of the pelvic urethra. Ampullae are enlargements of the ductus deferens that open directly into the pelvic urethra. The enlargement is the result of a dramatic increase in the mucosa within the ampulla. The mucosa of the ampulla forms numerous pockets. The boar does not have conspicuous ampullae. Seminal plasma is produced by the: Epididymis Ampulla Vesicular glands (seminal vesicles) Prostate gland Bulbourethral glands (Cowper's glands)  Vesicular glands are paired glands that are dorso cranial to the pelvic urethra. Vesicular gland secretions empty directly into the pelvic urethra. These glands were originally named the seminal vesicles. Early anatomists erroneously imagined that these glands were reservoirs for spermatozoa because there was a visual similarity between the secretion of these glands and ejaculated semen. While the vesicular glands do serve as a reservoir for their own secretions, they do not serve as a reservoir for spermatozoa. The vesicular glands have openings within the pelvic urethra that are separate from those of the ampullae. In bulls and boars the vesicular gland contributes to a large proportion of the ejaculate volume. The gross anatomical configuration of the vesicular glands varies significantly among species. In the bull and ram the vesicular glands are lobulated. In the boar they are well developed and contribute to a viscous, milky component of the seminal plasma. In the stallion the vesicular glands are elongated, hollow pouches. Prostate gland lies in close proximity to the junction between the bladder and pelvic urethra. There is great species variation with regard to shape and location. The prostate may have two structural forms. The first is a corpus prostate in which the prostate is outside of the urethralis muscle and is visible as a heart-shaped (boar), or an H-shaped (stallion) structure. The second type is a disseminate prostate in which glandular tissue is distributed along the dorsal and lateral walls of the pelvic urethra.  The disseminate prostate is sometimes referred to as the urethral gland. To observe the disseminate prostate one must make an incision in the pelvic urethra and expose the prostatic tissue. In the bull the prostate has two distinct forms and the corpus prostate is located near the neck of the bladder. In the boar the disseminate prostate is the major portion of the gland and the body of the prostate is often partially concealed by the vesicular glands. The ram does not have a prostatic body and its prostate is entirely disseminate. In contrast, the stal- lion has no disseminate prostate and the glands are characterized by two lateral lobes. The prostate is the only accessory sex gland in the dog and situated around the pelvic urethra at the neck of the bladder. In the tom, the prostate consists of four lobes that are dorsal to the pelvic urethra. The bulbourethral glands are paired glands located on either side of the pelvic urethra near the ischial arch. These glands are usually small and ovoid and are characterized by being quite dense due to the high degree of fibrous connective tissue within them. In the ram, bull and stallion these glands are small and buried under the bulbospongiosus muscle. The boar is the notable exception with regard to the size of the bulbourethral glands. They are very large and dense and lie on the surface of the caudal two thirds of the pelvic urethra. These glands produce a viscous secretion that is important because it provides the gel fraction of the ejaculate and causes the seminal plasma to coagulate following ejaculation.  Secretions of the accessory sex glands contain an immense variety of components and ions, most of which have not been assigned a function. In general, most substances found in blood, including hormones and enzymes, can be found in seminal plasma. It is beyond the scope of this book to detail all of the secretory products of the accessory sex glands. However, among the most unique are fructose that serves as an energy source for spermatozoa. The presence of these materials with regard to specific accessory sex glands varies among species. It should be emphasized that with the exception of fruc- tose as an energy source, the precise role of the other materials is not known. The accessory sex glands are dependent on tes- tosterone for full development and maintenance of their structure and function. In fact, the weights of acces- sory sex glands can be used as a bioassay for andro- gens. In the absence of androgens, the weights of the accessory sex glands will be quite low. In contrast, when androgens are present the weights of the acces- sory sex glands are normal and their secretory activi- ties are normal. The Penis is the Copulatory Organ The penis is composed of three parts. base (root) of the penis where it is attached to the ischial arch, the shaft (the main portion of the penis) and the glans penis that is the specialized distal end.  The glans penis is heavily populated with sensory nerves and is the homologue of the female clitoris. Stimulation of the glans penis is the primary factor initiating the mechanisms of ejaculation. The morphology of the glans penis varies significantly among species. For example, the glans penis of the tom is covered with spines.These penile spines are androgen dependent and disappear when orchidectomy (removal of the testicles) is performed. The purpose of the spines is not known but it has been pro- posed that these structures maximize vaginal stimulation during copulation and promote induction of ovulation. The glans penis of the alpaca contains a single stiff spiny appendage called the cartilaginous process. The function is not known but this modification can cause damage to the cervix and uterus if excessive copulation is allowed. The glans penis of the boar consists of a "corkscrew" configuration to enable penetration of the interdigitating prominences of the cervix. Bulls, boars and rams have a fibroelastic penis with limited erectile tissue encased in a fonexpandable, dense connective tissue structure (tunica albuginea). In species with a fibroelastic penis, there is a sigmoid flexure. This is an S- shaped configuration along the shaft of the penis. The sigmoid flexure allows the penis to be retracted inside the body (within the sheath) until erection occurs. Erection is stiffening without a significant change in diameter. The sigmoid flexure is maintained by a pair of smooth muscles known as the retractor penis muscles.  These are attached dorsally to the coccygeal vertebrae and attached ventrally to the ventrolateral sides of the penis. When contracted, the retractor penis muscle holds the penis inside the sheath. When relaxed, the penis protrudes. The shaft of the penis has an area of spongy, erectile tissue known as the corpus cavernosum that makes up the majority of the penile interior. In the ventral portion of the penis immediately surrounding the penile urethra is another area of spongy erectile tissue called the corpus spongiosum. Erection in the bull, boar, ram, stallion and camelids is brought about by a combination of relaxation of the retractor penis muscles and the rushing of blood into the corpus cavernosum and the corpus spongiosum. The mechanism of erection and ejaculation will be presented in Chapter 11. The penile shaft of stallions, dogs and men have large corporal sinusotids that fill with blood following sexual stimulation. The cavernous tissue in the dog consists of two morphologically distinct regions. These are the bulbus glandis and the pars longa glandis. The bulbus glandis forms a turgid bulb during erection that allows the "copulatory lock" during the final stages of copulation. The dog penis also has an os penis (baculum) that runs through the bulbus glandis and the pars longa glandis. The penile urethra and corpus spongiosum are housed by a groove in the os penis. Erection, Protrusion of the Penis and Ejaculation are Under Muscular Control The paired ischiocavernosus muscles, the muscles associated with the pelvic urethra and the penis, vary in size and form depending on the species. The ischiocavernosus muscles are relatively short paired muscles in the area of the root of the penis. These are strong muscles enclosing the crura that insert broadly on the lateral surface of the penis above the sigmoid flexure. They also connect the penis to the ischial arch. Muscles associated with the pelvic urethra and the penis are: Urethralis Bulbospongiosus Ischiocavernosus Retractor penis Urethralis- is a striated muscle that surrounds the pelvic urethra in a circular manner.The urethralis muscle is a thick, powerful muscle responsible for movement of seminal plasma and spermatozoa into the penile urethra. Bulbospongiosus muscle overlaps the root of the penis and extends down the caudal and ventral surfaces. In the boar, ram and bull it extends only part way down the penis. This muscle also covers the bulbourethral glands. The function of the bulbospongiosus muscles is to empty the extrapelvic part of the urethra.