Embedded Files
Mammalian Heart Dissection
Mammalian Heart Dissection
The structure of the mammalian heart is part of the IP and O-level syllabus. To explore and understand the structure of the mammalian heart better, students were previously required to buy and bring their own animal heart specimen and a dissection practical was conducted during lesson time.
external features of the heart
external features of the heart
The coronary arteries are visible when observing the external features of the heart.
The coronary arteries function to transport oxygenated blood rich in nutrients towards the heart muscles.
Aerobic respiration requires oxygen and glucose as the raw material to release energy required for muscular contraction of the cardiac muscles.
aortic valve
aortic valve
The aorta is the largest artery in humans, and functions to transport oxygenated blood away from the heart to all parts of the body.
The aortic valve (semi-lunar valve) is found in the aorta, and functions to prevent the backflow of blood from the aorta into the left ventricle during ventricular diastole.
longitudinal cross section of the heart
longitudinal cross section of the heart
Visible in this photo are the chambers of the heart. The walls of the left ventricle are much more muscular compared to the walls of the right ventricle.
Chordae tendineae, which are connective tissues that hold the atrial-ventricular valves in position are also visible here.
The septum separates the right and left side of the heart, thus preventing the mixing of oxygenated and deoxygenated blood.
Mammalian Eye Dissection
Mammalian Eye Dissection
Occasionally, students may also carry out the dissection of eyeballs when they are learning about the human eye. The specimens are usually mammalian eyes, however the eye dissection can be done with any eye ball, even those from a fish can be dissected (just that the structures will be smaller and a little harder to observe).
specimen
specimen
Normally the supermarkets do not sell stand alone eyeballs. This specimen was part of a pig's skull, where the eye ball was subsequently removed in class.
This is a timely reminder that one should treat your specimen with respect and care. Ultimately, an animal died and you are using part of its body for your dissection.
external features of the mammalian eye
external features of the mammalian eye
After the surrounding fat is carefully removed to show the eyeball, the optic nerve (which contains sensory and motor neurones) is normally found at the back of the eyeball.
cross sectional dissection of the eyeball
cross sectional dissection of the eyeball
Notice that the inside of the eyeball is black in colour; the choroid contains a dark coloured pigment. This dark coloured pigment ensures light rays are absorbed inside the eyeball completely and are not internally reflected.
crystalline & elastic lens
crystalline & elastic lens
When I first did my own eyeball dissection as a masters student, I was surprised to find that the lens was shaped like a tiny spherical marble. Somehow, I had this misconception that the lens would be in the shape of a contact lens?!
The elastic lens of the eye is able to change its shape in order to focus light rays sharply onto the retina. Surrounding the lens are the suspensory ligaments (dark coloured region in the photo), which hold the lens in position inside the eye.
Organ dissection
Organ dissection
I had the honour to observe another colleague conducting a Sec 4 Advanced Biology dissection class previously in 2018. It was definitely an eyeopening experience for me as I never had such an opportunity to witness or conduct such a complex dissection.
Students were working in groups, and they were given part of a male or female pig specimen. They had to carry out their dissection and answer various questions in their worksheet.
female specimen
female specimen
From left to right:
large intestine
urinary system
female reproductive system
close up of the female specimen
close up of the female specimen
The two kidneys (dark coloured organs), one of the kidneys is still connected to the urinary bladder (filled with urine) via the ureter.
The female reproductive system (middle) with the uterus clearly seen.
On the right, the last section of the large intestine clearly seen.
female reproductive system
female reproductive system
Close up of the female reproductive system of the pig. The ovaries, fallopian tube and uterus can be clearly seen in this photo. Check the diagram next to it for reference.
diagram of the female reproductive system
diagram of the female reproductive system
Initially, I was slightly baffled by the unusual shape of the uterus. Then I realised pigs give birth to multiple young each time, so the shape of the uterus allows the development of multiple piglets during each pregnancy.
male specimen
male specimen
From top to bottom:
large intestine
urinary bladder (urethra observable)
penis
diagram of the male reproductive system
diagram of the male reproductive system
This diagram has the same orientation of organs as that of the photo titled "male specimen".
Cross reference to aid in organ identification.
The urinary system
The urinary system
The kidneys, urinary bladder, together with the ureter and urethra consists of the urinary system found in mammals, including pigs and humans. The function of the urinary system is to produce urine (kidney), which is temporarily stored (urinary bladder) and eventually excreted to the surroundings out of the body.
longitudinal cross section of kidney
longitudinal cross section of kidney
The cortex (dark brown) clearly observable, with the pyramids in the medulla and the renal pelvis (light colour in the middle).
urinary bladder
urinary bladder
The urinary bladder functions to temporarily store urine. This muscular bag seen in the photo is partially filled with urine here.
Page updated
Google Sites
Report abuse