Biology

Scrotum and its contents: Testicles

len Alfred Ajibola - Tue, 25th February, 2020 @ 12:18 PM

Topics in Biology

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Academic Questions in Biology

Please click here to see all Questions and Answers

Male Reproductive System - Len Academy

From the above diagram, which of the organ below isn't a requirement for the male reproductive system?

  • A. Bladder

  • B. Ureter

  • C. Glans Penis

  • D. Testis

  • E. Bulbourethral Gland

  • F. Epididymis

A walnut shaped male accessory sex organ located between the bladder and penis is the _____.

  • A. Ductus Ejaculatorii

  • B. Bulbourethral Gland

  • C. Prostate Gland

  • D. Ductus Deferens

  • E. Seminal Vesicles

  • F. Epididymis

In a food chain, the primary consumers are classified under trophic level  _____.

  • A. Zero

  • B. One

  • C. Two

  • D. Three

  • E. Four

  • F. Five

Cold blooded animals are referred to as _____.

  • A. Homeotherms

  • B. Endotherms

  • C. Poilokitherms

  • D. Ectotherms

  • E. Thermotherms

  • F. None of the above

All reptiles are vertebrates.

  • A. True

  • B. False

_____ cells are responsible for the formation of osteoblasts.

  • A. Osteocytes
  • B. Chondrocytes
  • C. Chondroblasts
  • D. Osteoclasts
  • E. Osteoprogenitor cells
  • F. Osteoblastic

_____ is a bone that constitute the axial skeleton.

  • A. Clavicle
  • B. Scapula
  • C. Patella
  • D. Radius
  • E. Sternum
  • F. Femur

Which of the following is false concerning cartilages and bones?

  • A. Cartilage does not have a direct blood supply while bones have direct blood supply
  • B. The process of ossification replaces a cartilage to bone
  • C. The protein that makes up cartilage is called chondrin while that that makes up bone is called ossein
  • D. Cartilage grows from both ends while bones grow from one of its epiphysis
  • E. They both have living cells within them
  • F. Haversian system is absent in cartilage but present in bones



Scrotum and Testicles:

The scrotum or scrotal sac is visible on every male as it lies underneath the penis, hanging from the midline of the pelvic region just between both thighs. It is a part of the male external genitalia.

Please read an introduction to the male reproductive system here.

Inside the scrotal sac are two oval shaped testicles or testes (singular -> testis) which are responsible for the formation and storage of sperm. The process of sperm formation is referred to as spermatogenesis.


  • Sperm is the male gamete in humans and other animals while the egg or ova is the female gamete. You can think of a gamete as the sex cell. The union of both sex cells (sperm + ova) is termed fertilization. A zygote is formed immediately after fertilization. It is this zygote that develops into the embryo, then a foetus (or fetus) and eventually a neonate or newly born child.

The scrotum is located outside the body and that's ideal. This is so because the testis requires a temperature slightly lower than that of the normal body temperature (36.5oC) to properly form the sperm cells. In fact, this is the ideal reason why the testes descends from the abdominal cavity (inside the body) to the scrotum (outside the body). This external position of scrotum therefore presents a temperature reduction by -1oC to -7oC.


The scrotum is divided in its midline by the perineal raphe. The perineal raphe is present in males and females. It is visible as a midline seen on some parts of the human body.

The image below shows the scrotum, its internal contents and the perineal raphe:
Scrotum - Len Academy

You can read on seminal vesicles and bulbourethral glands here.


What are the Testicles?

The testicle is the male reproductive gland in humans (males) and all other male animals. Its primary function is to produce sperm and the male sex hormone 'testosterone'.

Generally, males have two testicles of similar sizes with both located within either half of the scrotum. Interestingly, the scrotal sacs are not always equal in length; and as a result, one of the testicle (or testis) typically extends farther downwards into the scrotum in relation to the other.


Inside the developing male embryo (in the mother's womb), the testicles begin their formation in the abdominal region. After 8 weeks of gestation, the testicles gradually descend from the abdomen into the scrotum via through a tube-like structure in the inguinal canal. For this reason, the testicles are located outside the body (scrotum) and this is crucial for sperm formation or spermatogenesis.


As a male, one may have observed that on cold days, the scrotum hang towards the body. Conversely, it tends to move downwards (away from the body) on warmer days. This is so because at cooler temperatures, the cremaster muscle contracts, moving both testes towards the body with a resultant rise in the scrotal temperature. Conversely, the cremaster muscle relaxes when the environmental temperature rises, ultimately pushing the testes away from the body.

Sperm is produced by the testes present within the scrotum; and the surrounding temperature is extremely important for it's formation. To this end, the cremaster muscles of the scrotum have got a great ability to contract and relax, thus aiding the testes to either move closer to the body or away from it; depending on the surrounding temperature.

Please read on homeostasis here.


Structurally, both testes are covered by a membranous sheet called the tunica albuginea. The testes comprises of very minute and highly coiled tubes called seminiferous tubules. The cells lining the seminiferous produces the male gamete or spermatozoa or sperm cells.

From the seminiferous tubules, the sperm is conveyed into a another tubular structure termed rete testis. The rete testis is located in the mediastinum testis.

Structures of the testes - Len Academy

The sperm cells are conveyed from the rete testis into the ductuli efferentes testis (efferent ducts), and then to the epididymis. The maturation of sperm cells occur in the epididymis.

From the epididymis, the sperm travels into the vas deferens and eventually the spermatic cord. The vas deferens therefore functions to transport sperm from the epididymis to the spermatic cord as they are eventually moved through the urethra and out of the external urethral orifice through a series of muscular contractions.


Meanwhile, understand that sperm and semen aren't the same thing. Sperm is the male sex cell (and it happens to be the smallest cell in the human body). It is exactly what meets and fertilizes the female sex cell (ova or egg). Ironically, the ova is the biggest cell in the human body.

Semen refers to the thick whitish (or slightly yellowish) and viscous fluid released from the penis. The process of releasing semen in males is termed ejaculation.

You can read on amazing facts in biology here.


During ejaculation, millions of sperm cells are introduced into the female’s vagina; and they swim upwards (towards the oviduct or fallopian tube in the female) with the aid of their tail-like structure called flagella.

Ejaculation is always accompanied with a characteristic feeling of pleasure. In fact, this pleasurable feeling is the climax of sexual excitement and it's referred to as orgasm.

Note: The sperm cells are present within the semen. This is shown in the image below:
Sperm vs Semen - Len Academy


In summary, the semen contains the following:

  • Sperm cells

  • Amino acids

  • Enzymes

  • Vitamin C

  • Zinc prostate specific antigen

  • Mucus

  • Prostagladins

  • Phosphatases

  • Silic Acid

  • Flavins

Understand that apart from the sperm cells, many of these components making up the semen are secretions from the male accessory reproductive glands.

Please read on the male accessory sex organs here.


Apart from the testicles, also found in the scrotum are:

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Pufferfish contain a toxin called tetrodotoxin. This makes them foul tasting and poisonous to predators. Tetrodotoxin is about 1,200 times more poisonous than cyanide, and there is enough toxin in one pufferfish to kill 30 adult humans. Unfortunately, there isn't any known antidote to this poison.

Interestingly, a delicacy in Japan (called fugu) is made from pufferfish. This meal is very expensive, and must be prepared by trained and licensed chefs. An improper preparation of fugu may lead to the customer's death. Sadly, such deaths are recorded annually

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An abnormally enlarged pituitary gland had resulted into Robert Wadlow's giant size.

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An artery is composed of three layers:

  • The outermost layer is termed tunica adventitia (or tunica external). It consist mainly of collagen fibres and connective tissues that anchors the arteries to other nearby tissues.

  • The middle layer is named tunica media. It is made up of smooth muscles and elastic fibres that supports the artery in conveying blood at high pressures.

  • The inner layer is called tunica intima (or tunica internal). It is lined by a smooth tissue called endothelium, and is made up of a fine network of connective tissues.

Please read on the layers of an artery here

All living organisms possess various features in order to survive in their environment. This is the concept of adaptation. As an instance, a fish is able to live in water because it has gills and fins.

Also, a camel is able to survive in the desert because it has large feet to aid walking on sand without sinking. It also has long eyelashes to help protect it from the blowing sand and wind.

Plants are also able to live in different habitats because they have the required adaptive features towards that habitat. For instance:

  • Plants that live in/on water are termed hydrophytes.

  • Plants that live on land with moderate amount of water are termed mesophytes.

  • Plants that live on deserts or arid lands are termed xerophytes.

The point is:

All organisms have various features on them that enables them adapt in their habitat

For a thing to be considered living, it must possess all the basic characteristics of life. These include:

  1. Movement

  2. Respiration

  3. Nutrition

  4. Irritability or Sensitivity

  5. Growth

  6. Excretion

  7. Reproduction

  8. Death

  9. Adaptation

  10. Competition

Please read the explanations on all the basic characteristics of life here

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This is the concept of anaerobic respiration

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Note: Habitat is a place where an organism live. It is of three types:

  • Terrestrial (Land)
  • Aquatic (Water)
  • Arboreal (Treetops)

You can read on food chain here