Reproductive System Overview - Anatomy & Physiology

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The Mare Uterus- Courtesy of A.Crook, Copyright RVC 2008

Introduction to the Reproductive System

Reproduction is the complex set of biological processes that result in the formation of a new organism. It is crucial, especially in our production animals, that we understand how these processes occur normally and have a good grasp of the role of hormones in this process. Pathology and disease are common within the reproductive system and can not only lead to a sick animal but also to a loss in production. In this section we hope to cover all the main processes in the domestic animals. This will lay a foundation to aid in the understanding of more potentially quite complex pathologies.

Puberty

Puberty is the process of aquiring reproductive capability, and age at onset of puberty varies from between species. There are several factors involved in triggering the onset of puberty, including body size, nutritional factors, day length, genetic factors and environmental and social factors. The onset depends on the ability of specific hypothalamic neurons to produce gonadotropin-releasing hormone (GnRH) in sufficient quantities to both promote and support gametogenesis. The hypothalamus itself is influenced by hormonal factors that are male or female specific.

Female Reproductive Tract and Reproductive Behaviour

The anatomy of the female reproductive tract includes the the external genitalia and vagina, the cervix, the uterus, the oviduct and the ovary. Female animals regularly enter a phase where they are sexually active and receptive to males; this is collectively known as the oestrous cycle. Some animals are able to reproduce all year round, but many have an anoestrus phase which requires a seasonal response for cycling to begin. In some species detection of seasonal cycling can be crucial to productivity.

Female animals have various behavioural and chemical signals which increase their attractiveness to males and others which signal their acceptance of attention from the male. Further cues indicate that the female is receptive to mating. Other reproductive female behaviours include maternal and nursing behaviour. In neurological terms sensory information from behavioural and chemical cues are processed by the hypothalamus, which induces the appropriate mating response via specific peptides which activate neurons in the midbrain and brainstem.

Male Reproductive Tract and Reproductive Behaviour

The anatomy of the male reproductive tract includes the penis, the testes, the epididymis and the accessory sex glands. Males of different species are often referred to by specific names which reflect their repoductive status. Males differ from females in the production of sperm which takes place from puberty onwards - unlike females where ova are produced prior to birth. The hormones controlling sperm production, or spermatogenesis are luteinising hormone (LH) and follicle-stimulating hormone (FSH).

The neurological pathways that control reproductive behaviour are similar to the female, but the response is male specific and includes pre-copulatory, copulatory and post-copulatory behaviour.

Fertilisation, Implantation and Early Embryonic Development

After mating has occured, sperm must travel along the female reproductive tract towards the uterus in order to fertilise the oocyte. The sperm enters the oocyte and the male and female pronuclei fuse and divide repeatedly to form the blastocyst.

• Implantation

• Sexual Differentiation

• Internal and External Genitalia Development

Gestation

• Reference Table of Gestation Lengths in Various Species

• Diagnosis of Pregnancy

• Maternal Recognition of Pregnancy

• Litter Sizes

• Placenta

• Maintaining Pregnancy

Parturition

• Normal Parturition

• Endocrine Control of Parturition

• Pharmacological Manipulation of Parturition

• Risks in Parturition

The Puerperium

• Overview of the Puerperium

• Myometrial Contraction and Expulsion of Lochia

• Involution & Endometrial Repair

• Resumption of Ovarian Function: for more information see 'Species Differences in the Puerperium' below.

• Elimination of Bacterial Contamination of the Reproductive Tract

• Factors Influencing the Puerperium

• Species Differences in the Puerperium

Lactation

• Overview of Lactation

• The Mammary Gland

• Endocrine Control

• Milk Composition and Biosynthesis

• Involution

• Links to Associated Pathology

Reproductive Technologies

• Semen Collection

• Artificial Insemination

• Multiple Ovulation and Embryo Transfer

• In Vitro Fertilization

• In Vitro Maturation

• Intracytoplasmic Sperm Injection

• Embryo Sexing

• Semen Sexing

• Embryo Splitting

• Nuclear Transplantation:Cloning

• Transgenic Animals

Camelids (LLamas & Alpacas)

• Female Anatomy
• Male Anatomy
• Breeding Cycle
• Mating
• Pregnancy Diagnosis
• Parturition
• Lactation & Care of the Newborn

Small Domestic Mammals

• Summary of Reproductive Characteristics for Small Domestic Mammals
• Guinea Pig
• Ferret
• Chinchilla
• Chipmunk
• Mouse
• Hamster
• Rabbit
• Rat
• Gerbil

Exotics

• Avian Reproductive Anatomy and Physiology

• Reptile Reproductive Anatomy and Physiology

• Amphibian Reproductive Anatomy and Physiology

• Fish Reproductive Anatomy and Physiology

Test yourself - Reproduction System flashcards

• Reproductive System Flashcards

References

• P.L Senger: Pathways to Pregnancy and Parturition,2nd Edition
• David E. Noakes,Timothy J. Parkinson,Gary C. W. England,Geoffrey H. Arthur: Arthur's Veterinary Reproduction and Obstetrics
• Bairbre O'Malley:Clinical Anatomy and Physiology of Exotic Species
• Dyce, Sack and Wensing: Textbook of Veterinary Anatomy, 3rd Edition
• Konig and Liebich: Veterinary Anatomy of Domestic Mammals, 3rd Edition
• Victoria Aspinall, Melanie Cappello: Introduction to Veterinary Anatomy & Physiology
• Gina Bromage: Llamas and Alpacas: A Guide to Management
• R.J. Roberts,Lydia Brown: Aquaculture for Veterinarians - Fish Husbandry and Medicine (Pergamon Veterinary Handbook)
• B.Young, J.W Heath: Wheater's Functional Histology, A Text and Colour Atlas

Creators of Reproductive Anatomy and Physiology Pages

• Amy Cartmel (RVC)
• Lois Wilkie (RVC)