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## What cells are found in bony tissue?

Arsala K.
Featured 3 months ago

Osteocytes are preferentially termed as bone cells.

#### Explanation:

However, bones contain four types of cells:

• Osteogenic or osteoprogenitor cells $\to$ stem cells(these are only bone cells that divide)
These are present in deep layer of periosteum and endosteum. These form and develop into osteoblasts.
• Osteoblasts $\to$ bone-forming cells
Osteoblasts are derived from osteogenic cells. These are present in growing portions of bone including periosteum and endosteum. These form new bones.
• Osteocytes $\to$ mature bone cells.
These are mature osteoblasts that become entrapped in the bone matrix. Osteocytes continue to form bone to some degree, which is important for maintaining the strength and health of the bone matrix.
• Osteoclasts $\to$ bone dissolving cells
These are present in endosteum lining the marrow cavities containing blood vessels and bone marrow. These break down bony matrix which is called as bone resorption. Osteoclasts are large multinucleated cells that are quite different from other bone cells. These are formed by the fusion of many cells derived from circulating monocytes in the blood, hence these are phagocytic.

Hope it helps...

## How does HIV infect T-lymphocytes?

Arsala K.
Featured 3 months ago

HIV can lodge itself on membrane receptor of T lymphocyte and then injects viral RNA and viral enzymes in host cell.

#### Explanation:

Human immunodeficiency virus abbreviated as $H I V$ is a host-specific retrovirus that targets the major components of human immune system i.e $T$-$l y m p h o c y t e s$ or $T$-$c e l l s$.

Infection cycle of HIV:

• Attachment:
Firstly the HIV virus attaches to the $C d 4$ receptor site on the T-cells. These fuse with the t-cell membrane and get entry into the cell's cytoplasm where they are uncoated.
• Reverse transcription and Integration:
HIV virus being a retrovirus has a special enzyme known as reverse trancriptase on the $R N A$ $\text{genome}$. This enzyme uses the $\text{viral RNA}$ as a template to make a strand of $D N A$ and then uses the DNA strand as a template to make a DNA double helix. Original viral RNA gets degraded.
The viral DNA integrates into the chromosomal DNA of T-cell of the host, now becoming a provirus.
• Translation:
The proviral DNA is transcribed into RNA which uses host cell's machinery to translate viral proteins to encase newly generated viral genome.
• Assembly and Release:
So, new capsids assemble around $\text{viral RNA}$ and reverse transcriptase molecules. And they bud off from plasma membrane of T-cell as mature HIV viruses, ready to attack more T cells.

Increasing number of Cd4 cells start to die due to HIV infection.

## What is the appendicular skeleton?

BRIAN M.
Featured 3 months ago

The Appendicular Skeleton in composed of all of the bones of the Arms and Legs and Girdles.

#### Explanation:

The Skeleton in vertebrates is divided into two parts: axial and appendicular. In human, there are 126 bones in appendicular skeleton.

The Appendicular Skeleton is composed of all of the bones of the arms (=fore limb), legs (=hind limb) and girdles to which limbs are attached. Girdle for attachment of arm is pectoral and that for leg is pelvic.

The Axial Skeleton is composed of the bones of the head, spinal column and thorax (=rib cage).

## What organ is responsible for the absorption of nutrients derived from the foods we eat?

Arsala K.
Featured 2 months ago

After hearing the word 'absorption' the first organ which hop into mind is small intestine. But wait! Because there are two other also:

Small Intestine $\to$ #90%#absorption.
Large intestine $\to$ about #5%# absorption.
Stomach $\to$ about #5%# absorption.

#### Explanation:

Absorption in Stomach
The role of stomach in absorption is not that salient. Mostly water $\left({H}_{2} O\right)$ and alcohol$\left({C}_{2} {H}_{5} O H\right)$, salt, and simple sugars can be absorbed directly through the stomach wall.

Stomach mainly facilitates absorption of vitamin ${B}_{12}$. However, most substances in our food need a little more digestion and must travel into the intestines before they can be absorbed.

Absorption in Small intestine
Small intestine is called as small because of its shorter diameter. But if we consider length, it's not at all small. It's about $\text{6-7 meters}$ long tube which is coiled in order to fit in smaller portion of abdomen. Maximum absorption of nutrients takes place in small intestine.

The paramount features of small intestine which make it spectacular absorbing agent of several nutrients are: $\textcolor{\mathmr{and} a n \ge}{\text{The internal wall (mucosa) is made }}$ $\textcolor{\mathmr{and} a n \ge}{\text{ up of folds, each of which has many tiny finger-like}}$ $\textcolor{\mathmr{and} a n \ge}{\text{ projections known as villi, on its surface.}}$ $\textcolor{g r e e n}{\text{Apical membranes of villi further form many hair}}$ $\textcolor{g r e e n}{\text{like outgrowths called microvilli and it appear as brush border under microscope.}}$ Total area of absorption in small intestine becomes incredible large due to infoldings, villi and microvilli*.

Villi are structurally adapted to absorb maximum nutrients at faster rate. For example: villi are single cell thick, thus nutrients can easily cross their permeable membranes to get into bloodstream & villi are also supplied with rich network of capillaries and also contain vessels known as lacteal of lymphatic system.

Small intestine absorbs almost all the nutrients i.e. amino acids, glucose, bile salts, fatty acids and glycerols and is also crucial in the absorption of fat-soluble vitamins (Vitamin A, D, E and K) & vitamin ${B}_{12}$. Absorbed fat and fat soluble vitamins enter lacteal.

Absorption in Large intestine or Colon
There are trillions of bacteria, yeasts, and parasites living in our intestines, mostly in the colon. Over 400 species of organisms live in the colon.

Large intestine is primarily involved in absorption of water. However, it also absorbs some ions and nutrients released by gut bacteria, specially several vitamins e.g vitamin K. It also absorbs water which remains in the undigested food.

Hope it helps...

## How do they diagnose placenta accreta?

Shray Patel
Featured 1 month ago

Doctors diagnose placenta accreta through an ultrasound.

#### Explanation:

Placenta accreta occurs when the placenta becomes deeply attached to the uterine wall and can result in severe blood loss during childbirth. Placenta Accreta may demonstrate vaginal bleeding in some cases, but is usually detected during routine ultrasounds. Treatment for placenta accreta usually involves a C-section, followed by a hysterectomy (surgical removal of the uterus).

Understanding the Placenta
The placenta is an organ that develops during pregnancy that provides both nutrients and oxygen to the fetus. The placenta is connected to the wall of the uterus (womb), and nutrients are absorbed through the placental membrane.

What is Placenta Accreta?
Placenta accreta is a condition where the lining of the placenta becomes too deeply attached to the uterine wall. When delivering the baby, this can result in severe blood loss, because instead of detaching from the womb like a normal placenta, the placenta accreta remains partially attached to the uterine wall during childbirth.

## What are the different body systems in human body and what are their functions?

Arsala K.
Featured 1 month ago

There are total $11$ systems in human body containing their specific organs hence are called as organ systems.

#### Explanation:

These are muscular system, digestive system, integumentary system, skeletal system, circulatory system, respiratory system, lymphatic system, endocrine system, excretory system and reproductive system. All these systems contain their specific organs. However, these systems are somehow related to each other.

Breif concept to their functions is as follows:

Muscular system $\to$ provide movements.

The muscular system, in vertebrates, is controlled through the nervous system, although some muscles, like cardiac muscle & muscles in stomach walls, can be completely autonomous. And others like, skeletal muscles are under conscious control.

Muscles run throughout the human body. Each muscle has a specific name according to it's location or function. All these muscles work and render human body to function normally. For example, when you want to play flute you have to pucker your lips, you can do so with the help of Orbicularis oris, a muscle surrounding the lips.

Digestive system $\to$ breakdown the food and absorb nutrients from it.

Food we eat is the body's source of fuel. Nutrients in food give the body's cells the energy they need to operate. Before food can be used it has to be broken down into tiny little pieces so it can be absorbed and used by the body. In humans, proteins need to be broken down into amino acids, starches into sugars, and fats into fatty acids and glycerol. The whole process of digestion is aided by chemical and nervous coordination.

Integumentary system $\to$ act as a barrier, protect the inner stuff of body, regulate body temperature and also eliminate waste(e.g sweat).

The outermost layer of skin i.e epidermis is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out.

And the layer that lies below epidermis i.e dermis performs major functions and also nourishes epidermis. It contains a number of structures including blood vessels, nerves, hair follicles, smooth muscle, glands and lymphatic tissue. It paly major role in thermoregulation.

The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves.

Skeletal system $\to$ supports the body and protect the internal organs(e.g rib cage protect heart and lungs).

Muscular and skeletal system works together to provide movements. Besides, skeletal system provide proper shape to our body. Without this system, human body can never be so organized as it is.

Circulatory system $\to$ help to transfer blood, nutrients, hormones, oxygen and other gases to and from different body parts.

The circulatory system is extremely important in sustaining life. It’s proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide, waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells, of the lymphatic system.

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. Heart oxygenates that blood. Then $\textcolor{red}{\text{ arteries}}$(except pulmonary arteries) supply the oxygenated blood to various organs of the body. So it means that blood travels from different chambers of the heart all the time. Muscular system is also involved in this circulation if blood. The autonomous cardiac muscles relax and contract to help the heart in pumping blood.

Respiratory system $\to$ station of gaseous exchange i.e ${O}_{2}$ in and $C {O}_{2}$ out of the body.

The respiratory tract is the path of air that starts from the nasal cavity and end in smaller alveoli in lungs. It's major role is in breathing, no doubt an inevitable process. Besides, respiratory system also regulates blood $p H$ and control body temperature.

Nervous system $\to$ help all the body parts to communicate with each other via electrical and chemical impulses.

Nervous system is involved in Nervous coordination . Nervous system is divided into central nervous system(CNS) & peripheral nervous system(PNS). CNS represents the largest part of the nervous system, including the brain and the spinal cord, Together, with the peripheral nervous system (PNS), it has a fundamental role in the control of behaviour.

Nervous system communicate with several other body systems. For example: Even when we haven't started eating, our brain starts telling our digestive organs i.e pancreas and stomach via nerves about the expected entry of food. And pancreas stimulated by neural signals produce about #20%# of it's total secretion because of this stimulus. Skeletal muscles also need neural inputs to start contraction.

Lymphatic system $\to$ It plays a vital role in natural defense of body against infections.

The lymphatic system helps Defend the body against foreign invaders. It destroys the bacteria and viruses through lymphocyte and macrophages with present within lymph nodes. Lymphatic system is involved in absorption of fat globules which are released by interstitial cells and the products of digestion of fats are absorbed.

Spleen filters the blood. It destroys aged red blood cells and foreign particles from blood via it's lymphocytes & macrophages.

Endocrine system $\to$ It also help different body parts to communicate by secreting chemical substances called hormones.

Endocrine system is involved in Chemical coordination. It constitutes $20$ endocrine glands/tissues. These glands secrete hormone which are poured in bloodstream. From blood these are transported to the target tissues where they perform their particular work. For example: When the sugar level in blood drops then pancreas(an endocrine gland) secrete glucagon which works to increases glucose in blood.
Endocrine system is involved in controlling growth, metabolism, sexual development, maintaining homeostasis etc...

Endocrine and nervous system work together and aid other organ systems to perform their functions.

Excretory system $\to$ help body to get rid of wastes.

Excretion is the process of eliminating, from an organism, waste products of metabolism and other materials that are of no use. The most salient organs of this system are kidneys. Kidneys with the help of their functional units i.e nephrons, maintains an appropriate fluid volume by regulating the amount of water that is excreted in the urine, regulate concentrations of various electrolytes in the body fluids, maintain normal $p H$of the blood and maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism. They do this by separating urea, mineral salts, toxins, and other waste products from the blood. They also do the job of conserving water, salts, and electrolytes. At least one kidney must function properly for life to be maintained.

Reproductive system $\to$ aid in the production of new individual.

All living things reproduce. This is something that sets the living apart from non-living. Even though the reproductive system is essential to keeping a species alive, it is not that essential for keeping an individual alive.

As in case of sexual reproduction, the specific traits are inherited from parents to their offspring. So, in this case reproduction is important in conservation of certain genetic makeups. While if we talk about asexual reproduction then its merely involved in producing new individual. Because there is no exchange of genetical materials in asexual reproduction.

Hope it helps!

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