- Integrative Control of Energy Balance and Reproduction in Females
- Cortisol influence on testicular testosterone secretion in domestic cat: An in vitro study
- Male Reproductive Anatomy
- Overview of Systemic Pharmacotherapeutics of the Reproductive System
In many animals the shape of the penis is adapted to match that of the vagina. Some have spines, warts or hooks on them to help keep them in the vagina and copulation may be extended to help retain the semen in the female system. Sperm are made up of three parts: a head consisting mainly of the nucleus, a midpiece containing many mitochondria to provide the energy and a tail that provides propulsion see diagram Some may be dead while others are inactive or deformed with double, giant or small heads or tails that are coiled or absent altogether.
- The Devil, The Ghost and Will Anderson!
- Freely available.
- The Biology of Early Influences.
- Inborn Disorders of Sphingolipid Metabolism. Proceedings of the Third International Symposium on the Cerebral Sphingolipidoses.
- Antenatal Care Module: 4. Hormonal Regulation of the Female Reproductive System.
- Fractals and Chaos: An Illustrated Course.
When there are too many abnormal sperm or when the sperm concentration is low, the semen may not be able to fertilize an egg and the animal is infertile. Sperm do not live forever. They have a definite life span that varies from species to species. They survive for between 20 days guinea pig to 60 days bull in the epididymis but once ejaculated into the female tract they only live from 12 to 48 hours. When semen is used for artificial insemination, storage under the right conditions can extend the life span of some species.
In many species the male can be artificially stimulated to ejaculate and the semen collected. It can then be diluted, stored and used to inseminate females. For example bull semen can be diluted and stored for up to 3 weeks at room temperature. Unfortunately the semen of chickens, stallions and boars can only be stored for up to 2 days.
Dilution of the semen means that one male can be used to fertilise many more females than would occur under natural conditions. There are also advantages in the male and female not having to make physical contact. It means that owners of females do not have to buy expensive males and the possibility of transmitting sexually transmitted diseases is reduced. Routine examination of the semen for sperm concentration, quality and activity allows only the highest quality semen to be used so a high success rate is ensured.
Since the lifespan of sperm in the female tract is so short and ova only survive from 8 to 10 hours the timing of the artificial insemination is critical. The female reproductive system consists of a pair of ovaries that produce egg cells or ova and fallopian tubes where fertilisation occurs and which carry the fertilised ovum to the uterus. Growth of the foetus takes place here.
Integrative Control of Energy Balance and Reproduction in Females
The cervix separates the uterus from the vagina or birth canal, where the sperm are deposited see diagram Note that primates like humans have a uterus with a single compartment but in most mammals the uterus is divided into two separate parts or horns as shown in diagram Ovaries are small oval organs situated in the abdominal cavity just ventral to the kidneys. Most animals have a pair of ovaries but in birds only the left one is functional to reduce weight see below. The ovary consists of an inner region medulla and an outer region cortex containing egg cells or ova.
These are formed in large numbers around the time of birth and start to develop after the animal becomes sexually mature. A cluster of cells called the follicle surrounds and nourishes each ovum. The ovarian cycle refers to the series of changes in the ovary during which the follicle matures, the ovum is shed and the corpus luteum develops see diagram Numerous undeveloped ovarian follicles are present at birth but they start to mature after sexual maturity.
In animals that normally have only one baby at a time only one ovum will mature at once but in litter animals several will. The mature follicle consists of outer cells that provide nourishment. Inside this is a fluid-filled space that contains the ovum. A mature follicle can be quite large, ranging from a few millimetres in small mammals to the size of a golf ball in large animals.
Cortisol influence on testicular testosterone secretion in domestic cat: An in vitro study
It bulges out from the surface of the ovary before eventually rupturing to release the ovum into the abdominal cavity. Once the ovum has been shed, a blood clot forms in the empty follicle. This develops into a tissue called the corpus luteum that produces the hormone progesterone see diagram If the animal becomes pregnant the corpus luteum persists, but if there is no pregnancy it degenerates and a new ovarian cycle usually. Diagram When the ovum is shed the nucleus is in the final stages of meiosis cell division.
It is surrounded by few layers of follicle cells and a tough membrane called the zona pelluc ida see diagram The oestrous cycle is the sequence of hormonal changes that occurs through the ovarian cycle. These changes influence the behaviour and body changes of the female see diagram The first hormone involved in the oestrous cycle is follicle stimulating hormone F. It stimulates the follicle to develop. As the follicle matures the outer cells begin to secrete the hormone oestrogen and this stimulates the mammary glands to develop. It also prepares the lining of the uterus to receive a fertilised egg.
Ovulation is initiated by a surge of another hormone from the anterior pituitary, luteinising hormone L. This hormone also influences the development of the corpus luteum, which produces progesterone , a hormone that prepares the lining of the uterus for the fertilised ovum and readies the mammary glands for milk production.
If no pregnancy takes place the corpus luteum shrinks and the production of progesterone decreases. This causes FSH to be produced again and a new oestrous cycle begins. For fertilisation of the ovum by the sperm to occur, the female must be receptive to the male at around the time of ovulation.
These signs are turned off again at the end of the oestrous cycle. During the oestrous cycle the lining of the uterus endometrium thickens ready for the fertilised ovum to be implanted. If no pregnancy occurs this thickened tissue is absorbed and the next cycle starts. In humans and other higher primates, however, the endometrium is shed as a flow of blood and instead of an oestrous cycle there is a menstrual cycle. The length of the oestrous cycle varies from species to species. In rats the cycle only lasts 4—5 days and they are sexually receptive for about 14 hours.
Dogs have a cycle that lasts 60—70 days and heat lasts 7—9 days and horses have a day cycle and heat lasts an average of 6 days. Ovulation is spontaneous in most animals but in some, e. This is called induced ovulation.
Male Reproductive Anatomy
Only a few animals breed throughout the year. This includes the higher primates humans, gorillas and chimpanzees etc. These are known as continuous breeders. Most other animals restrict reproduction to one or two seasons in the year- seasonal breeders see diagram There are several reasons for this.
Fertilization IV. Cleavage V.
Maintenance of the Preimplantation Embryo References Anatomy of the Uterus III. Implantation IV. Growth of the Conceptus and Formation of the Placenta V. Immunological Problems of Pregnancy References Hormonal Mechanisms during Pregnancy and Parturition I. Hormonal Mechanisms in Parturition References Mammary Growth and Lactation I. Milk Synthesis V.
Milk Ejection References Environmental Factors Affecting Reproduction I. Nutritive Influences Upon Reproduction I. Infectious Diseases Influencing Reproduction I. Bacterial Infections III. Virus Infections IV. Protozoan Infections V. Domestic Birds III. Domestic Mammals IV. Reproduction in Domestic Fowl I. Sex Development III. The Male Reproductive System V.
Reproduction References Subject Index. Powered by. You are connected as.
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Overview of Systemic Pharmacotherapeutics of the Reproductive System
Superoxide dismutase and taurine supplementation improves in vitro blastocyst yield from poor-quality feline oocytes. Theriogenology , 85 5 : A rare case of testicular disorder of sex development in a dog 78, XX; SRY-Negative with male external genitalia and detection of copy number variation in the region upstream of the SOX9 gene. Sexual Development , 10 2 : Modification of membrane cholesterol and its impact on frozen-thawed chicken sperm characteristics.