Grade 12 Human Reproduction Part 1 Male reproductive organs Flashcards
What makes up the male reproductive organs?
- Primary sex organs - the testis / testes in scrotum
- Ducts - epididymis, sperm duct (vas deferens) and urethra
- Accessory glands e.g. prostrate
- External genitalia - penis
To simplify: Testes, Tubules for the transport of sperm, accessory glan
What is the scrotum and what is its function?
**A sac of skin that ecloses the testis.
**Functions: **
* Temperature regulator - keeping testis 2 - 3 degrees lower than body temperature ( for formation of fertile sperm).
* Protects the testis
What is the testis?
- Primary male sex organs - pair of **testes **
- Two oval structures, suspended outside the body in the scrotum
- Oval shaped gland, about 5cm in length
- Divided internally into compartments or small lobules
- Each lobule contains several closely packed, convoluted seminiferous tubules - 250m in each testis
- Tubules - lined with special cells, namely germinal epithelium.
- Epithelium cells can divide and give rise to sperm (male gametes) in a process called - spermatogenesis
- Between the tubules (connective tissue) are groups of endocrine cells - the interstitial cells / cells of Leydig = Produce male hormone testosterone
- A few germinal epithelium cells develop into l**arger columnar cells - Sertoli cells = provide food for sperm
I
Discuss the function of the testis:
- Sperm production
- Testosterone - male sex hormone - development of secondary sexual characteristics
List the tubules for the transport of sperm (4)
- Epididymus
- Vas deferens (sperm duct)
- Ejaculatory duct
- Urethra
What is the epididymus?
Seminiferous tubules join to form the epididymis where they:
* mature to become motile and fertile
* are stored for several months (after which they are broken down by the epithelial cells of the epididymis and re-absorbed into the body
* situated at the back of the testes and lined with a mucous membrane
Explain the function of the epidiymis: (2)
- Stores sperm produced in testes - mature inside until ready to become motile and fertile and fertilise ovum
- Mucous membrane lining epididymis secretes a substance that, together with peristaltic movements of tubule walls, facilitate movement of sperm
What is the sperm duct / vas deferens?
- Muscular sperm duct = continuation of epididymis, which passes through abdominal cavity and opens in urethra
- Forms a swelling just before it joins the urethra = ampulla
What is hte function of the sperm duct / vas deferens?
- Transports sperm - by means of peristaltic movements, from epididymis to urethra
- Ejaculation
What is the ejaculatory duct?
The ampulla of the vas deferens leads to a muscular tubule, the ejaculatory duct.
What is the function of the ejaculatory duct?
The smooth muscle fibres in the duct contract, forcing the contents of the duct (semen) along the urethra to the exterior.
I.e. to ejaculate
What is the urethra?
The duct at the end of the uro-genital system leading to the exterior.
What is the function of the urethra?
- Forms a common duct for the transportation of semen and urine.
- These two processes never occur together.
LIst the accessory glands:
- Seminal vesicles
- Prostate gland
- Cowper’s glands
Explain seminal vesicles:
- Two sac-like structures connected by a tubule to the lower end of the ampulla.
- Lined with a mucous membrae that secretes a yellow-ish, sticky substance.
What is the function of the seminal vesicles?
Secretion of mucous membrane provides fructose, main source of food for sperm.
What is the prostrate gland?
- **Plumb-sized **
- Surrounds urethra at the base of the bladder - where ejaculatory ducts join the urethra
- Conical gland
- Secretes a milky alkaline liquid, the prostrate fluid, which gives semen its characteristic smell
Discuss the function of the prostrate gland:
Secretes prostrate fluid - that:
1. ensures maximum sperm motility (certain enzymes)
1. protects sperm against low pH (acidity) in the urethra and vagina
What are Cowper’s glands?
**Two small glands on either side of the urethra - just below the prostrate gland.
What are the functions of Cowper’s glands?
- Secretion = greater motility of sperm
- Clears the urethra of urine residue - neutralise acidic urine
- Lubricates the head of the penis - prevents mechanical damage during ejaculation
Explain what the penis is:
- Male sex organ
- Consists of shaft + head region
- Cone-shaped head - glans penis
- Partially covered by foreskin - remove through circumcision
- Shaft is divided up into three columns of erectile tissue - Corpus carvernosa (2 columns) , corpus spongiosum
- Erectile tissue in these columns become filled with blood during arousal due to increased blood pressure and blood flow = erection
Explain the three columns that the shaft of the penis is divided into:
- **Corpus cavernosa **- 2 columns of erectile tissue that form the upper part of the penis
- Corpus spongiosum - 1 smaller column of erectile tissue that surrounds the urethra on the lower part of the penis. Ensures that the urethra remains open during erection for the passage of semen.
What mechanism brings about an erection of the penis?
- Dilation of the dorsal and central arteries supplying blood to the penis.
- This allows more blood to fill the three spongy erectile tissue chambers (columns), causing the penis to lengthen and stiffen.
What is the function of the penis?
- **Deposits semen with sperm **into the female’s vagina during copulation.
- Sperm are brought **closer to the egg **for fertilisation - increases chances of fertilisation.
What is distinctive about the HUMAN penis?
- Human male has no erectile bone (baculum) in the penis - relies on engorgement / filling up with blood to reach erect state.
- **Not attached to abdominal wall **but hangs free - in contrast to other mammals
What is semen?
Consists of:
* Sperm - from the testis
* Seminal fluid from the sperm duct and accessory glands e.g. prostate
What is average volume of semen for an ejaculation?
2.5 - 5ml semen
50 million - 150 million sperm per ml!
Thus around 700million per ejaculation.
If less than 20 million per ml - infertile
What is the difference between erection and ejaculation?
Erection = stiffening of the penis
Ejaculation = expulsion of semen
Discuss puberty in boys:
- Time period during which sex organs develop and gametes are produced in a boy
- Puberty starts around 12 years
- Hypophysis secretes the **hormone LH (luteinising hormone) **- which stimulates the cells of Leydig to produce male hormone, testosterone
- Hypophysis also releases the **hormone FSH (follicle stimulating hormone) **- stimulates the process of **spermatogenesis **together with testosterone.
What effect does testosterone have re secondary sexual characteristics?
- Increased muscle mass
- englargement of skeletal muscle and broadening of shoulders
- deeper voice - increase in size of larynx
- enlargement of penis and testes
- sperm production
- sexual drive
- sweat production
- increase in facial and body hair - moustache, chest hair, armpit and pubic and leg hairs (about 13 - 14)
- oily skin (may develop acne)
- growth spurt - appetite
- behavioural changes - mood, emotional outbreaks, changed sleeping patters
List, in order, all the structures a sperm travels through from where it is made until its release from the body. Also mention the gland it passes through. (See Page 92 - Mind Action) (5 marks)
Name distinctive human male sexual activities:
- Sexually fertile all th time unlike most mammalian species
- Nocturnal emissions - wet dreams
- Mating not confined to period of female ovulation - to increase pair bonding, care for young
