# Make the internet a better place to learn

3

## Heart is a pumping device for blood. Is there a separate blood supply for heart wall?

Arsala K.
Featured 2 months ago

Heart gets its blood supply from coronary arteries.

#### Explanation:

Our heart pumps the blood throughout the body i.e from head to toe.

$\textcolor{b l u e}{\text{Veins}}$(except pulmonary veins) carry the oxygen poor blood from different organs and give it to the heart.

Deoxygenated blood from right side of heart is sent to lungs where most of the carbondioxide diffuses out and oxygen diffuses in. Oxygenated blood returns to left side of heart.

$\textcolor{red}{\text{Arteries}}$(except pulmonary arteries) supply the oxygenated blood to various organs of the body.

So it means that blood travels through different chambers of the heart all the time, but this blood is of no nutritional use to the heart. It is just the blood which the heart has to pump.

Heart muscle definitely needs its own blood supply for oxygen and nutrition in order to keep beating continuously. This blood supply is provided to the heart by $\textcolor{red}{\text{coronary arteries}}$.

Coronary arteries lie on outer surface of heart. There are two coronary arteries i.e right coronary artery and left coronary artery.

Both these arteries arise from base of aorta.

Right coronary artery divides into right posterior descending artery (that turn to posterior part)and marginal branch. Left coronary artery divides into left descending anterior branch and left circumflex branch. Both these arteries supply oxygen rich blood to cardiac or heart muscles. And thus these are the arteries which fulfill the nutritional demand of the heart. That's why these are also known as Cardiac arteries.

Hope it helps...

2

## What are the three distinct types of blood vessels? Describe each in few sentences.

Aleksandra C.
Featured 2 months ago

Arteries, veins, capillaries.

#### Explanation:

Arteries

• Carry blood away from the heart and deliver oxygen-rich blood to the tissues of the body (except for the pulmonary artery which carries deoxygenated blood to lungs)
• Have very elastic wall which help to withstand the pressure created as the heart pumps the blood
• Each artery is lined by smooth tissue and has three layers:

outer tunica externa, comparatively thicker middle layer tunica media and inner tunica interna/endothelium.

Veins

• Carries deoxygenated blood towards the heart (except pulmonary veins which carries oxygenated blood from lungs)
• Have thinner nonelastic wall
• Unlike to arteries they are under low pressure and rely on muscle contractions to return blood to the heart
• Have valves which prevent the blood from flowing in the opposite direction
• Also have three layers:

Capillaries

• Smallest of the body's blood vessels
• Have very thin wall made of only endothelium
• Perform oxygen, carbondioxide, nutrients and waste exchange between blood and tissues easily
• They are connection between veins and arteries

5

## How is a neuron adapted to perform its function?

Aleksandra C.
Featured 1 month ago

The nerves cells are rather long which enables communication with distant body parts. The dendrites allow for communication with other neurons. Myelin surrounding the axon of a neuron acts as an insulator.

#### Explanation:

The above example is a very general description. In fact, neurons can be categorized into three groups based on their function:

Sensory neurons:

• Carry impulses from the receptors (cells that detect the stimuli i.e. heat or pressure) to the central nervous system (CSN).

• They have longer dendrites and shorter axons due to carrying of impulses from sensory organs to the spinal cord or brain.

• In general, sensory neurons are very long cells as they have to carry the impulses from the body to the place where the response occurs.

Motor Neurons

• Carry impulses from the CSN to the effector (cells responding to the stimuli i.e organs, muscles)

• They have long axons and shorter dendrites due to the passage of impulses from spinal cord or brain to the effector organs/cells.

Relay neurons

• Co-ordinate responses

• They are known as link neurons in the CNS due to their function which is to link sensory neurons with the motor neurons

2

## How many diaphragms are there in our body?

Jane
Featured 2 months ago

$5$

#### Explanation:

These are the main diaphragms present in our body,which acts as partitioning agent as well as weight bearer.

1 .THE DIAPHRAGM : Present at the junction of thoracic and abdominal cavity.

2 .PELVIC DIAPHRAGM : Present at the junction of abdomen proper above and pelvic cavity below.

3 .UROGENITAL DIAPHRAGM : Present at the junction of greater pelvis above and perineum below.

4. DIAPHRAGMA ORIS : This is a muscle bulk formed by the myelohyoid muscle which bears the weight of the tongue.

5. DIAPHRAGMA SELLA : It covers the pituitary gland,present inside the middle cranial fossa.

1

## What might if we had simple squamous instead of stratified squamous epithelium on our skin? happen?

Lanilyn L.
Featured 2 months ago

Die

#### Explanation:

Note that the skin is the major barrier between the inside and outside of your body.

• The outermost layer of the skin — the epidermis is a keratinized, stratified, squamous epithelium. Superficial layer of epidermis is made of dead cells.
• Melanocytes which produce melanin are found in the stratum basale layer. Melanin protects cells from damage by UV, by producing a 'veil' over the nucleus.
• Lamellar bodies are secreted by Keratinocytes which fuse with cell membrane and an impermeable barrier is formed on skin.
• This along with keratin laden dead cells of superficial layer prevent entry of microbes through skin surface, unless there is any injury on the skin.

Without these defense mechanisms, water and moisture would leak out, we’d be very susceptible to pathogens crossing the single squamous epithelium (SSE) and we’d be subjected to the daily harmful UV rays of the sun.

I want to reiterate the important functions of the skin.

Protection : it protects against UV light, mechanical, thermal and chemical stresses, dehydration and invasion by micro-organisms.

Sensation : skin has receptors that sense touch, pressure, pain and temperature.

Thermoregulation : various features of the skin are involved in regulating temperature of the body. For example sweat glands, hair, and adipose tissue.

Metabolic functions: subcutaneous adipose tissue is involved in production of vitamin D, and triglycerides.

(There’s a purpose to why SSE are located in the capillaries, lung alveoli, glomeruli, mainly because this lining functions for rapid diffusion of gases, nutrients and wastes rather than protecting the host from gargantuan external threats.)

1

## Does anyone know how thick the skin (epidermis and dermis ) is on the back of the neck at the base?

Ernest Z.
Featured 2 months ago

The thickness is about 1.6 mm.

#### Explanation:

The skin has two principal layers: the epidermis and the dermis.

The dermis contains two layers: the papillary layer and the reticular layer.

The thickness of the skin differs at various body sites.

The thinnest skin is on the eyelids. It is about 0.5 mm thick.

The thickest skin is on the heels of the feet, where it can be up to 5 mm thick.

Here is a chart showing the thickness (in millimetres) of skin on the neck (an average of 121 persons).

$\boldsymbol{\text{Area"color(white)(mmmm)"Epidermis"color(white)(m)"Papillary"color(white)(m)"Reticular"color(white)(m)"Total}}$
$\underline{\boldsymbol{\textcolor{w h i t e}{m m m m m m m m m m m m m l l} \text{layer"color(white)(mmml)"layer} \textcolor{w h i t e}{m m m m m}}}$
$\text{Upper neck} \textcolor{w h i t e}{m m m l l} 0.11 \textcolor{w h i t e}{m m m m} 0.12 \textcolor{w h i t e}{m m m m l} 1.44 \textcolor{w h i t e}{m m m} 1.67$
$\text{Midneck} \textcolor{w h i t e}{m m m m m} 0.08 \textcolor{w h i t e}{m m m m} 0.07 \textcolor{w h i t e}{m m m m l} 1.41 \textcolor{w h i t e}{m m m} 1.55$
$\text{Lower neck/}$
$\text{Décolletage} \textcolor{w h i t e}{m m m l} 0.07 \textcolor{w h i t e}{m m m m} 0.06 \textcolor{w h i t e}{m m m m l} 1.20 \textcolor{w h i t e}{m m m} 1.33$

3

## Why it is said that, Diptheria licks the nerves but eats the heart?

Jane
Featured 2 months ago

Diphtheria is a disease caused by Corynebacterium diphtheriae

This bacterium can cause a lot of manifestations like respiratory diptheria, cutaneous diptheria, invasive or disseminated diphtheria.

In case of respiratory diphtheria the patient mainly suffers from mechanical complications (asphyxia/choking) due to appearance of a tough membrane on tracheal lining but some systemic side effects too occur due to its toxin.

These conditions are manifested as myocarditis (an inflammatory condition of the myocardium, here it is sterile in nature as the bacterium itself doesn't reach the myocardium) and descending type of peripheral polyneuropathy (degeneration of peripheral nerves which is centripetal in nature).

Neurologic complications appear during 1st or 2nd week of illness and begins with dysphagia (problem in swallowing), and goes away after the disease is gone.

But cardiac damage is permanent and death may occur due to circulatory failure.

That's why it is said that Diphtheria licks the nerves but eats the heart.

1

## A male person having genes for childhood polycystic kidney disease was married to a lady who was diagnosed as carrier for colorblindness,they had 3 children,if two of them were normal,calculate the chance of the 3rd children to suffer from these diseases?

Jane
Featured 2 months ago

For boys the chance is 50% and for girls 0%

None will suffer from Childhood Polycystic Kidney Disease

#### Explanation:

After we have finished the pedigree analysis we can see that the couple can have $8$ types of children,i,e the 3rd children can be any of the $8$ types shown below.

out of the $4$ types of girls,one is absolutely normal,one is carrier of CPKD,one is carrier of colorblindness and the last one is carrier of both.

So,out of $4$ none will be suffering from these two diseases,so probability of suffering of the 3rd child as a girl is $0$

Now,considering $4$ boys, one is also absolutely normal,one is carrier of CPKD,one is colorblind and the last one is carrier of CPKD and colorblind at the same time.

So,out of $4$ only $2$ will be colorblind,so probability is 2/4=1/2=50%

NOTE: None of the children will suffer from CPKD as all of them will receive one dominant normal gene from mother.

5

## I got this project for school, and one of the largest questions are: Why can you faint if you stand still for too long? I don't really know how to formulate myself in that sense... so if you we're able to explain - it would be a massive help

Ernest Z.
Featured 2 months ago

Here's what I find.

#### Explanation:

What is fainting?

Fainting is a brief, sudden loss of consciousness.

You become unresponsive and may fall.

The medical term for fainting is syncope (from Greek syn "together" + kope
"a cutting short") [of blood flow to the brain].

How does standing for a long time cause fainting?

It is harder for the heart to pump blood up to the brain than down to the toes.

When you stand for a long time, especially in the heat, blood from your upper body can pool in your legs.

The blood supply to the brain decreases, and you faint.

What is happening in the body?

Your body has a feedback system of sensors in the arteries leading to the brain.

These sensors control many nerve and hormone signals that change your heart rate, constrict your blood vessels, and maintain your blood pressure.

When the blood pools in your legs, the feedback system triggers your heart rate and blood pressure to drop suddenly.

The blood flow to your brain decreases.

How is the brain involved?

The brain needs a constant supply of sugar and oxygen.

If blood flow drops, the brain goes into an energy-conserving shutdown.

It sends signals to your nerves and muscles to stop.

You lose consciousness and slump to the ground.

5

## What does it mean to be ticklish?

Ernest Z.
Featured 1 month ago

If you are ticklish, you quickly feel uncomfortable when someone touches your skin to make you laugh.

#### Explanation:

Being ticklish is both a neurological response and a learned behaviour.

Tickling as a neurological response

Being tickled stimulates your hypothalamus which, in turn, activates your fight-or-flight and pain responses.

When someone tickles you, you may laugh, not because you are having fun, but because you are having an autonomic nervous response.

In fact, the body movements of a ticklish person are similar those of someone in pain.

The automatic response may have developed early in our evolution.

The most ticklish parts of the body (feet, chest, neck, armpits) are the most vulnerable during combat.

We laugh and squirm when we're touched there because it's an evolutionary mechanism for self-defence.

We automatically try to get the tickler's hands away from these zones,

Tickling as a learned behaviour

Babies learn to laugh in response to tickling during their first few months of life.

The one-on-one activity during tickling opens the door to other forms of social interaction.

Thus, tickling also becomes a mechanism for social bonding.

It helps forge relationships between family members, friends, and lovers.