PHYSIOLOGY TEST 2

Generic Reproductive System

Females create an egg, known as a oocyte or ovum, which can be fertilised by the production of spermatozoa or sperm from the male reproductive system.

Reproductive System Purpose

To ensure that the species continues, with this process allowing for the creation of haploid gametes that combine to form an offspring.

Gamete

Refers to sex cells that are produced by the male and female organs, which are known as gonads. Can be haploid or diploid, with haploid meaning half the number of normal chromosomes so only 23, whereas diploid has the full set of 46.

Gonads

Produce gametes and important hormones. Males have testes that produce sperm and females that have ovaries that produce oocyte which becomes ovum.

Ducts

Designed to receive and transport gametes to the location for them to combine and hopefully form an embryo.

Accessory reproductive glands

Glands and organs that will secrete fluids into the ducts and structures of the reproductive system to aid in reproductive processes.

Perineal Structures

External genetalia that can be visibly seen from the outside.

Epididymis

A tightly coiled tube that is bound to the posterior border of each testis. At the tail end the coil starts to straighten out and joint to the ductus deferens. It’s for storage and maturation of the sperm, which takes 18 hours to 10 days, with it takin up to two weeks to move through approximately 7 metres of its coiling. It also monitors and adjusts fluid composition for fluid produced by the seminiferous tubules. Finally, it acts as a recycling centre with the lining being columnar epithelial cells with cilia that absorb and secrete necessary products to maintain the optimum environment. It also and mainly recycles damaged spermatozoa and cell debris. Spermatozoa will travel here after release into seminiferous tubules.

Ductus deferens or Vas Deferens

Part of the spermatic cord and extends from the testes through to the ejaculatory duct. This part act as storage for mature sperm, which can sit inactive for several months until ejaculation.

Ovaries

Where oocyte is produced. These are then released into fallopian tubes, which connects to the uterus. The oocyte can then be fertilised by sperm, and 9 months later there will be birth through the cervix and the vaginal canal.

Meiosis

Production of gametes in reproductive organs. So, sperm and oocytes, with both having 23 chromosome pairs. These then combine to form 46 chromosomes or a diploid cell. There are two stages. The second is where the division of gametes into final haploid cells happen to be ready to fuse together. The first step, a single cell begins and duplicates chromosomes as normal, however, instead of lining up and dividing, the chromones form a product known as a tetrad, with all 4 chromosomal pairs joined together and divided in the first process, allowing genetic variation to occur. These cells then divide evenly into two daughter cells. In stage 2 there is pure division of the current chromosomal pairs. So once division occurs, there will be 4 haploid gametes.

Male Meiosis

Produces 4 immature gametes that will go through the process of development and maturation known as spermiogenesis, which produces 4 fully functional spermatozoa.

Purpose of male reproductive system

To produce haploid spermatozoa (male gametes) and deliver these gametes into the uterus fallopian tubes of the female reproductive system.

Testes

Endocrine function (meaning they produce hormones, specifically androgens) that produces spermatozoa.

Male urethra

Passage for urine from bladder. As well as where spermatozoa/semen leaves. The process of ejaculating the semen through the urethra is vital for transporting metazoa to the female reproductive system.

Male reproductive accessory glands

Seminal gland, prostate gland, and bulbourethral gland. These will add in fluids that will mix with the sperm as they move through the ductus deferens and beginning of ejaculatory duct to create semen.

Seminal Glands/Vesicles

Present underneath the bladder and secretes largest quantity fluid for semen production, around 60% of the volume of semen. These fluids contain sugars for sperm metabolism, with ducts draining into ductus deferens. The fluids are quite viscous and alkaline which helps neutralise the acid from the prostate secretions and acids in the vagina as well. Also contains fructose for energy for sperm, prostaglandins which help stimulate smooth muscle contraction in reproductive tracts, and also fibrinogen which helps semen form a temporary clot in the vagina after ejaculation to hold it in there.

Prostate Gland

Muscular organ. that circles that urethra and contains a large amount of glandular tissue. It secretes a secretion known as prostate fluid (which is thin, acidic and milky coloured) which is then mixed with the fluids and the sperm coming from the ejaculatory duct. It’s about 20 to 30% of the volume of the semen. It contains lots of compounds which help with sperm motility and viability. One key compound is seminal plasmin which is an antibiotic kind of protein that helps kill different types of bacteria such as coli which helps protect the urinary tract in males.

Bulbourethral Glands

Underneath the prostate and empties a thick alkaline mucus into the urethral lumen, which mixes with other fluids and the sperm moving through the urethra as well. It helps neutralise urinary acids so it doesn’t damage the sperm, and also helps lubricate the tip of the penis during sexual intercourse.

Penis

Structure that allows introduction of semen into the female vagina during sexual intercourse. It is normally in a flaccid state, which is relaxed. During sexual arousal, blood flow will increase into the erectile tissues of the penis which will cause an erection.

Scrotum

Sac of skin made of muscle and connective tissue layers, containing testes. Divided into two separate chambers, with each one containing one of the testes and associated epididymis and spermatic cord. It houses the male gonads. They are external for temperature regulation, with normal development of spermatozoa requiring a cooler temperature of 1.1 degrees, with muscle layers contracting and relaxing to move testes either towards or away from body.

Testes

Made of lobules which contain highly coiled tubercles known as seminiferous tubercles. This is where sperm production takes place. These seminiferous tubercles empty into a structure knows as the mediastinum of the testes, which connect straight into a passageway of tubercles known as the rete testes. These empty through efferent ductules which empty into the epididymis structure. The semiferous tubercles is where sperm production or spermatogenesis takes place. They’re surrounded by connective tissue capsules, with lots of blood vessels. Theres also specialised cells known as the interstitial cells of Leydig, which line the lobules and have the important function of producing the sex hormone known as androgens or testosterone.

Spermatogenesis

Production of sperm. Begins in outermost layer of the seminiferous tubule, with the sperm cell moving physically closer to the lumen (inside the tubercle) with each step, where the sperm will eventually be released and sent through these structures of the testes into the epididymis.

Spermatogonium

A stem cell that will eventually grow and divide to become a sperm. When it divides it specifically forms a spermatocyte, which will undergo meiosis to allow for the maturation and production of spermatozoa.

Cells that support spermatogenesis

Interstitial endocrine cells or interstitial cells of Leydig, and nurse cells.

Male nurse cells

There are multiple nuclei throughout the seminiferous tubercle. These cells envelope around the primary and secondary spermatocytes as they produce and go through the process of meiosis to create multiple sperm.

Seminiferous tubercle cell wall

Where the process that nurse cells go through to produce a mature sperm cell takes place.

Steps of spermatogenesis

Starts with division of a stem cell, which are the spermatogonium. These then grow and divide into a primary spermatocyte through the process of mitosis, to produce two daughter cells. One of these daughter cells will continue to remain as spermatogonium, whilst the other will begin differentiation into a primary spermatocyte, where it will under meiosis. It will divide into two secondary spermatocytes which will undergo meiosis 2, dividing and differentiating into spermatids, which are the immature male gametes. These spermatids will then continue to differentiate into spermatozoa through spermatogenesis which occurs in the innermost layer of the seminiferous tubercles, which is supported by nurse cells. Once finished the spermatozoa will be released into the lumen of the tubercle, although not fully matured yet. It will then undergo spermiogenesis.

Maturation Process of Sperm Cells

This will continue on as the spermatozoa move through structures including the epididymis and ductus deferens. Spermatozoa cant fully function before being mature, meaning they can’t move their flagella, tail or things like that. This process is spermiogenesis.

Spermatogenesis vs. Spermiogenesis

Spermatogenesis is the division process which includes the full process of mitosis, meiosis and maturation in the seminiferous tubercles. Spermiogenesis is the maturation of the spermatids into fully functioning sperm.

Spermiogenesis

The maturation process of spermatids into the structure known as sperm. The spermatid must transform into mature spermatozoa with a head, neck and long flagellar tail. This process occurs in the cytoplasm of the nurse cells lining and creating the seminiferous tubule wall, with the spermatozoa staying linked to the tubules until structural transformation.

Acrosome

Feature of matured sperm that is important for the ability of spermatozoa to get through the layers protecting the ova during fertilisation. It is developed from parts of the Golgi apparatus, which have kind of flattened out and fused together to form the acrosomal coating that covers the outside of the sperm head.

Body of sperm

Quite small and light as it is primary a carrier for genetic material, so its where the nucleus remains. Unlike other cells, it doesn’t contain an endoplasmic reticulum or normal Golgi apparatus and lysosomes or any other organelles. That’s because the specific function of spermatozoa doesn’t require these organelles to function normally.

Neck of spermatozoa

Contains mitochondria arranged around microtubules that will provide the ATP and energy for the spermatozoa to move the tail and survive.

Tail of spermatozoa

A long fibrosus tail known as the flagellum. It is the only flagellum produced by the human body. It moves in a whip like kind of corkscrew motion that propels the cell from one location to another. Vital.

Movement of Sperm

After spermatozoa are semi matured from spermiogenesis, they’re released into the lumen of the seminiferous tubule. Then they’re moved through the structures of the seminiferous tubule and then into the epididymis. It then travels to ductus deferens. Takes us to ejaculatory duct and then urethra, which is how sperm is delivered into females.

Ejaculatory Duct

Short passage that empties directly into the urethra during ejaculation

Semen

Secretions are added as sperm moves through the final portion of the ductus deferens and ejaculatory duct and urethra. Fluids are added as they’re important for nourishing the sperm. They contain antimicrobials and all sorts of things to help look after the sperm. These fluids and sperm combined is what we call semen.