Topics in BiologyTropical savanna explained with its characteristics Ecological pyramid explained with its importance and limitations Hindbrain: Medulla Oblongata and its features Food web explained with examples Biology Scheme of Work, SS1, First Term Biology Scheme of Work, SS1, 2nd Term Biology Scheme of Work, SS1, 3rd Term Male accessory sex organs: Seminal vesicles and bulbourethral glands Scrotum and its contents: Testicles Brain: Introduction to the human brain Forebrain: Lobes of the cerebrum and their functions Cerebellum: Parts and functions of the cerebellum Midbrain: Division and functions of the midbrain Negative feedback mechanism in homeostasis Arterial disorders explained with their causes Types of desert and their characteristics Characteristics of tropical rainforest Swamp forest: What are swamp forests? Characteristics of swamp forests Savanna biome: Concept of the savanna
Academic Questions in Biology
In a food chain, the primary consumers are classified under trophic level _____.
Cold blooded animals are referred to as _____.
F. None of the above
All reptiles are vertebrates.
_____ cells are responsible for the formation of osteoblasts.
_____ is a bone that constitute the axial skeleton.
Which of the following is false concerning cartilages and bones?
A diagram showing the movement of energy through a food chain is called a _____.
Which of the following is NOT a part of the wrist bones (or carpal bones)?
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.
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.
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:
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.
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.
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.
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:
In summary, the semen contains the following:
Zinc prostate specific antigen
Understand that apart from the sperm cells, many of these components making up the semen are secretions from the male accessory reproductive glands.
Apart from the testicles, also found in the scrotum are:
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Amazing facts in Biology
99% of a panda's diet is bamboo. They may eat fish or other small animals occasionally
When attacked by insects, lima beans plant will often command parasitic wasps to their defence.
When the leaves of the lima bean's leaves are eaten by insects, the plant gives off a substance that signals parasitic wasps to swam in, destroying its enemies (the leaf-eating insects) in the process
Frogs drink water through their skin
Armadillos are western mammals known for their unique armor-like shell which are bulletproof
Although zebras are known for their characteristics black and white stripes, we still have some polka-dotted zebras
Charles Darwin is a British naturalist and biologist who contributed greatly into the study of evolution. According to research, he frequently ate the animals he studied
Lungs are the only human organ that can float on water
Unlike most snakes that lay eggs, anacondas give birth to live babies
A shrimp's heart is in its head
Women have more pain receptors than men
NOTABLE POINTS IN Biology
For a thing to be considered living, it must possess all the basic characteristics of life. These include:
Irritability or Sensitivity
During strenuous exercises like sprinting or running, your body may actually work in the shortage of oxygen. During this time, your body owes oxygen (called oxygen debt) and it must be replenished or repayed after the exercise is stopped. This is why you breathe excess of oxygen after you stopped the exercise.
This is the concept of anaerobic respiration
A food chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.
Note: Habitat is a place where an organism live. It is of three types:
The term Biology originated from two Greek words. They are:
Bios: means life.
Logos: means knowledge or to study.
Biology can therefore be defined as the study of life
Anything that has life is generally considered as a living organism (or organism). All living organisms must be able to carry the following activities:
Irritability or Sensitivity
The above listed points are often regarded as the basic characteristics of life. You can memorize them using the acronym -> MR. NIGER DAC.
The gas used in the manufacture of food by plants is Carbon dioxide or Carbon(IV)oxide or CO2
Plants manufacture food through a process called photosynthesis.
It is noteworthy to state that plants are the only orgnisms that take away CO2 from the atmosphere