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Wednesday, March 18, 2015

Cytoplasm definition and function

The Cytoplasm is the entire cell except the nucleus. Proteins are made in the cytoplasm, and many of the cells life activities take place there.

Many tiny structures called organelles are located in the cytoplasm.

Each has a particular job to do. These organelles are called mitochondria, lysosomes, the endoplasmic reticulum, centrioles, and Golgi bodies.

Mitochondria - What is mitochondria?

Mitochondria are the power producers of the cell. A cell may contain hundreds of mitochondria. These sausage-shaped structures produce almost all the energy the cell needs to live and to do its work.

Lysosome function and definition

Lysosomes are small, round bodies containing many different enzymes, which can break down many substances. For example, lysosomes help white blood cells break down harmful bacteria.

Endoplasmic Reticulum

Endoplasmic Reticulum is a complex network of membrane-enclosed spaces in the cytoplasm. The surfaces of some of the membranes are smooth. Others are bordered by ribosomes—tiny, round bodies that contain large amounts of RNA. Ribosomes are the cells manufacturing units. The proteins the cell needs in order to grow, repair itself, and perform hundreds of chemical operations, are made on the ribosomes.

Centrioles

Centrioles look like two bundles of rods. They lie near the nucleus and are important in cell reproduction.

Golgi Bodies

Golgi Bodies, also called Golgi complex or Golgi apparatus, consist of a stack of flat, bag-like structures that store and eventually release various products from the cell.

Vertumnus and Pomona Roman Gods Names

Vertumnus was the god of garden and field produce. He personifies the change of seasons, and that process of transformation in nature by means of which the leaf-buds become developed into blossoms, and the blossoms into fruit.
The change of seasons is symbolized in a myth which represents Vertumnus as metamorphosing himself into a variety of different forms in order to gain the affection of Pomona, who so loved her vocation that she abjured all thoughts of marriage. He first appears to her as a ploughman, typifying Spring; then as a reaper, to represent Summer; afterwards as a vine-gatherer, to indicate Autumn; and finally as a gray-haired old woman, symbolical of the snows of Winter; but it was not until he assumed his true form, that of a beautiful youth, that he succeeded in his suit.
Vertumnus is generally represented crowned with wheat-sheaves, and bearing in his hand a cornucopia.

POMONA

Pomona was the goddess of orchards and fruit-trees, who, according to Ovid, cares not for woods or streams, but loves her gardens and the boughs that bear the thriving fruit.
Pomona, who typifies Autumn, is represented as a lovely maiden, laden with branches of fruit-trees.

Text:
Myths and Legends of Ancient Greece and Rome
Author: E.M. Berens
Published: 1880

The Project Gutenberg E-Book
Produced by Alicia Williams, Keith Edkins and the Online
Distributed Proofreading Team at http://www.pgdp.net

A guy who got into IIT and Google.

Naga Naresh Karutura has just passed out of IIT Madras in Computer Science and has joined Google in Bangalore. You may ask, whats so special about this 21-year-old when there are hundreds of students passing from various IITs and joining big companies like Google?

Naresh is special. His parents are illiterate. He has no legs and moves around in his powered wheel chair.

Ever smiling, optimistic and full of spirit; that is Naresh. He says, "God has always been planning things for me. That is why I feel I am lucky." Read why Naresh feels he is lucky.

Childhood in a village

I spent the first seven years of my life in Teeparru, a small village in Andhra Pradesh, on the banks of the river Godavari . My father Prasad was a lorry driver and my mother Kumari, a house wife. Though they were illiterate, my parents instilled in me and my elder sister (Sirisha) the importance of studying.

Looking back, one thing that surprises me now is the way my father taught me when I was in the 1st and 2nd standards. My father would ask me questions from the text book, and I would answer them. At that time, I didnt know he could not read or write but to make me happy, he helped me in my studies!

Another memory that doesnt go away is the floods in the village and how I was carried on top of a buffalo by my uncle. I also remember plucking fruits from a tree that was full of thorns.

I used to be very naughty, running around and playing all the time with my friends.. I used to get a lot of scolding for disturbing the elders who slept in the afternoon. The moment they started scolding, I would run away to the fields!

I also remember finishing my school work fast in class and sleeping on the teachers lap!

January 11, 1993, the fateful day

On the January 11, 1993 when we had the sankranti holidays, my mother took my sister and me to a nearby village for a family function. From there we were to go with our grandmother to our native place. But my grandmother did not come there. As there were no buses that day, my mother took a lift in my fathers friends lorry. As there were many people in the lorry, he made me sit next to him, close to the door.

It was my fault; I fiddled with the door latch and it opened wide throwing me out. As I fell, my legs got cut by the iron rods protruding from the lorry. Nothing happened to me except scratches on my legs.

The accident had happened just in front of a big private hospital but they refused to treat me saying it was an accident case. Then a police constable who was passing by took us to a government hospital.

First I underwent an operation as my small intestine got twisted. The doctors also bandaged my legs. I was there for a week. When the doctors found that gangrene had developed and it had reached up to my knees, they asked my father to take me to a district hospital. There, the doctors scolded my parents a lot for neglecting the wounds and allowing the gangrene to develop. But what could my ignorant parents do?

In no time, both my legs were amputated up to the hips.

I remember waking up and asking my mother, where are my legs? I also remember that my mother cried when I asked the question. I was in the hospital for three months.

Life without legs

I dont think my life changed dramatically after I lost both my legs. Because all at home were doting on me, I was enjoying all the attention rather than pitying myself. I was happy that I got a lot of fruits and biscuits.

I never wallowed in self-pity

The day I reached my village, my house was flooded with curious people; all of them wanted to know how a boy without legs looked. But I was not bothered; I was happy to see so many of them coming to see me, especially my friends!

All my friends saw to it that I was part of all the games they played; they carried me everywhere.

Gods hand. I believe in God. I believe in destiny. I feel he plans everything for you. If not for the accident, we would not have moved from the village to Tanuku, a town. There I joined a missionary school, and my father built a house next to the school. Till the tenth standard, I studied in that school.

If I had continued in Teeparu, I may not have studied after the 10th. I may have started working as a farmer or someone like that after my studies. I am sure God had other plans for me.

My sister, my friend

When the school was about to reopen, my parents moved from Teeparu to Tanuku, a town, and admitted both of us in a Missionary school. They decided to put my sister also in the same class though she is two years older. They thought she could take care of me if both of us were in the same class. My sister never complained.

She would be there for everything. Many of my friends used to tell me, you are so lucky to have such a loving sister. There are many who do not care for their siblings.

She carried me in the school for a few years and after a while, my friends took over the task. When I got the tricycle, my sister used to push me around in the school.

My life, I would say, was normal, as everyone treated me like a normal kid. I never wallowed in self-pity. I was a happy boy and competed with others to be on top and the others also looked at me as a competitor.

Inspiration

I was inspired by two people when in school; my Maths teacher Pramod Lal who encouraged me to participate in various local talent tests, and a brilliant boy called Chowdhary, who was my senior.

When I came to know that he had joined Gowtham Junior College to prepare for IIT-JEE, it became my dream too. I was school first in 10th scoring 542/600.

Because I topped in the state exams, Gowtham Junior College waived the fee for me. Pramod Sirs recommendation also helped. The fee was around Rs 50,000 per year, which my parents could never afford.

Moving to a residential school

Living in a residential school was a big change for me because till then my life centred around home and school and I had my parents and sister to take care of all my needs. It was the first time that I was interacting with society. It took one year for me to adjust to the new life.

There, my inspiration was a boy called K K S Bhaskar who was in the top 10 in IIT-JEE exams. He used to come to our school to encourage us. Though my parents didnt know anything about Gowtham Junior School or IIT, they always saw to it that I was encouraged in whatever I wanted to do.. If the results were good, they would praise me to the skies and if bad, they would try to see something good in that. They did not want me to feel bad. They are such wonderful supportive parents.

Life at IIT- Madras

Though my overall rank in the IIT-JEE was not that great (992), I was 4th in the physically handicapped category. So, I joined IIT, Madras to study Computer Science.

Here, my role model was Karthik who was also my senior in school. I looked up to him during my years at IIT- Madras. He had asked for attached bathrooms for those with special needs before I came here itself. So, when I came here, the room had attached bath. He used to help me and guide me a lot when I was here.

I evolved as a person in these four years, both academically and personally. It has been a great experience studying here. The people I was interacting with were so brilliant that I felt privileged to sit along with them in the class. Just by speaking to my lab mates, I gained a lot..

There are more good people in society than bad ones

July 28, 2008

Words are inadequate to express my gratitude to Prof Pandurangan and all my lab mates; all were simply great. I was sent to Boston along with four others for our internship by Prof Pandurangan. It was a great experience.

Joining Google R&D

I did not want to pursue PhD as I wanted my parents to take rest now. Morgan Stanley selected me first but I preferred Google because I wanted to work in pure computer science, algorithms and game theory.

I am lucky. Do you know why I say I am lucky?

I get help from total strangers without me asking for it. Once after my second year at IIT, I with some of my friends was travelling in a train for a conference. We met a kind gentleman called Sundar in the train, and he has been taking care of my hostel fees from then on.

I have to mention about Jaipur foot. I had Jaipur foot when I was in 3rd standard. After two years, I stopped using them. As I had almost no stems on my legs, it was very tough to tie them to the body. I found walking with Jaipur foot very, very slow. Sitting also was a problem. I found my tricycle faster because I am one guy who wants to do things faster.

One great thing about the hospital is, they dont think their role ends by just fixing the Jaipur foot; they arrange for livelihood for all. They asked me what help I needed from them. I told them at that time, if I got into an IIT, I needed financial help from them. So, from the day I joined IIT, Madras , my fees were taken care of by them. So, my education at the IIT was never a burden on my parents and they could take care of my sisters Nursing studies.

Surprise awaited me at IIT

After my first year, when I went home, two things happened here at the Institute without my knowledge.

I got a letter from my department that they had arranged a lift and ramps at the department for me. It also said that if I came a bit early and checked whether it met with my requirements, it would be good.

Second surprise was, the Dean, Prof Idichandy and the Students General Secretary, Prasad had located a place that sold powered wheel chairs. The cost was Rs 55,000. What they did was, they did not buy the wheel chair; they gave me the money so that the wheel chair belonged to me and not the institute.

My life changed after that. I felt free and independent. Thats why I say I am lucky. God has planned things for me and takes care of me at every step.

The world is full of good people.

I also feel if you are motivated and show some initiative, people around you will always help you. I also feel there are more good people in society than bad ones. I want all those who read this to feel that if Naresh can achieve something in life, you can too

Shuttle to Launch Plug and Play Micro Labs

On Monday, Space Shuttle Discovery will carry equipment and experiments to the International Space Station (ISS). However, one payload is particularly exciting.
As part of a joint venture between Kentucky Space (a non-profit space research collaboration based in Kentucky) and the Houston-based company NanoRacks, a new type of standardized micro-laboratory will be launched and installed on the space station during the 13-day STS-131 mission.

Standardized Labs, Faster Science
Small laboratories have been installed aboard the space station before (such as the space butterfly outreach experiment, organized by Baylor College of Medicine in Houston), but this is the first attempt at designing and building a standardized, cheap and lightweight technology to be used by multiple organizations for a variety of microgravity science experiments.
"When the rack is installed, youd plug in the lab via USB," Kris Kimel, President of Kentucky Space, told me during a phone call on Friday.
USB (or Universal Serial Bus) devices are standard pieces of kit in the computing world, so by giving "CubeLabs" this capability, "they basically become plug and play laboratories," Kimel said, emphasizing the convenience of the NanoRack/CubeLab concept.
Up to 16 individual CubeLabs can be installed on each NanoRack, each capable of carrying out independent experiments.

One of the CubeLabs (Kentucky Space).

The most appealing thing about these mini laboratories is that they are very lightweight, so they can be easily unplugged, stowed and transported to and from the station by the next available flight. Currently, space station experiments are often too unwieldy, forcing research groups to wait for long periods of time before they can retrieve their experiments from space, no matter how interesting or important their science results may be.
Also, due to their design and function, NanoRacks allow a higher pace of microgravity experimentation, stimulating more "high risk" experiments, potentially boosting low-cost space research.

A Space Science Mash-Up
The NanoRack concept is proving to be so popular with NASA that Kimel expects to have a second NanoRack installed on the ISS in May after being launched as part of the STS-132 mission, shuttle Atlantis final scheduled flight before retirement. By this summer, there will be 32 kg (70 lb) of research mass contained inside the two installed NanoRacks, and more are expected.
"Almost all of our space tech is built by students. NASA has very stringent quality controls, so this is a huge achievement," he added.
Indeed, this is the kind of space collaboration that NASA is looking for since President Obamas redirection of space exploration priorities.
When speaking with Kimel, I was especially interested to hear how Kentucky Space operates. "Its kind of a mash-up," he told me when describing the range of groups that made this endeavor possible. There are university researchers, students, enthusiasts and now, by teaming up with NanoRacks LLC, they have a strong partnership with a profit-making organization.
Kentucky Space and NanoRacks will offer their system to research groups to house their own experiments (while still providing CubeLab support), but Kimel pointed out that his organization will be carrying out experiments of their own, focusing on the microgravity biomedical field.

Space Research can be Ubiquitous
So could this be the future of space research? Kimel thinks so, after all, you dont often associate the state of Kentucky with cutting edge space research! Space is ubiquitous; once launch and technology costs are pushed lower, a wider range of non-profit and for-profit organizations can get involved, no matter where they are located and whether or not they are funded by governments.

The NanoRack plus CubeLab (Kentucky Space/NanoRacks).

"Since NASAs new focus on entrepreneurial space activities, well see more organizations like Kentucky Space joining up with companies to get low-cost technology into space," he said.
"Space is like the personal computer industry of the 1980s."
This is a good analogy, especially when remembering the infamous prediction by Thomas Watson, chairman of IBM in 1943: "I think there is a world market for maybe five computers."
In the 1980s the computer industry exploded with advanced technology, cheap hardware and companies competing to dominate the market, making computers so affordable, anyone could own one. This formed the basis of the home computer industry today where computers are installed in every facet of our lives.
Once again, micro-technology is shrinking the size of components and private industry is making launch costs cheaper. When combined, they are stimulating a potential explosion of space research, the start of which we are seeing today. In 50 years time, saying, "I think there is a world market for maybe five space research platforms," may sound just as absurd as Watsons 1943 prediction -- a mindset that ultimately led to the demise of IBMs dominance over the computer industry.

Next Up: Orbital "CubeSats"
Kentucky Space is no stranger to putting stuff into space either. On March 27, 2010, one of their own suborbital "CubeSats" was successfully launched by a Terrier-Improved Malamute rocket from NASA Wallops Flight Facility, Va. (video below).
The first orbital CubeSat is scheduled to be launched with NASAs Glory mission in November 2010.
All in all, the NanoRack/CubeLab concept is a very exciting one, opening the doors to entrepreneurial space research, joining the upward trend of commercialized spaceflight while getting students, researchers, entrepreneurs and NASA to work together toward a common goal.

My sister was staying with me last weekend and she asked what was that strange picture book in my office. Displayed on my shelves are The Long Journey of Mister Poop, Pat the Beastie, and The Festival of Bones, among others, so I needed a bit more than that to answer her. Turns out she was referring to Duck, Death and the Tulip, a book I intended to review but hadnt gotten around to yet.

The reason is that its not your usual picture book, and I wanted to do it justice. The story is simple. Death, wearing a fashionably long plaid coat and bearing a black tulip, comes to stay with Duck. Understandably nervous, Duck asks, "Are you going to make something happen?" But no. "Life takes care of that," Death tells her. The two pal around, going to the pond, perching high in a tree. Duck wonders about dying and Death listens to her speculate. Winter comes, and one night Duck lies down. She does not get up. Death gently places her body in the river, the tulip resting on her chest.

The last lines are:

For a long time he watched her.
When she was lost to sight, he was almost a little moved.
"But thats life," thought Death.

Written and illustrated by Wolf Erlbruch, a German author, (and beautifully translated by Catherine Chidgey), the books simple text and sparse, elegant illustrations combine to create a moving yet unsentimental treatise on death. It also has a sly, deadpan humor throughout, as when Duck first notices Deaths presence. "Duck was scared stiff, and who could blame her?"

The book is not for every child, but I so wish it was around when my daughter was six or so. She went through a stage when the thought of death panicked her, just looking at her reflection in the mirror could set her off. This book, with its calm, unblinking look at death, might have eased her fears and helped our discussions. Who knows? She may still get a copy.

Duck, Death and the Tulip
by Wolf Erlbruch
Gecko Press, 38 pages
Published: 2008

Australia Unit Learning the States and Territories

During our unit on Australia, my son (7yrs old), learnt about Australian geography including the states, their capital cities, the flags for each state as well as the flora emblem, the different animal and bird emblem of each state as well as significant landmarks (built and natural) for each state.

I started with a book called Flags and Emblems of Australia by Jill Bruce to learn about the emblems of each state. I went searching and found some printable Australian state flags, printable floral emblems for each state and territory and printable colouring pictures of animal and bird emblems of Australia. I also got some Australian travel brochures from our local travel agency to use the pictures for cutouts.

I made up two printable facts sheet, one for Australian State Facts (like the one below) and another for Australia Territories Facts so we could record the information we had researched. These facts sheets can be used for writing an information report on a selected Australian state or territory.

Below is an example of how my son recorded his researched information about the Northern Territory using the printables as well as pictures from the travel brochures.

Some other great printables I found are from Our Worldwide Classroom. Below is an example of the Australian States Printable 3-part cards that are available from Our Worldwide Classroom so hope over and check them out! While you are there you might want to download their printable Australia Day Mini Unit as well as their Australian Flags that are also 3-part cards.

Following these activities, we made our own Australia map which helped us as we learnt about each state and territories. You can download a copy of our FREE printable Australia map from here.

If you would like to see more learning ideas and resources about Australia, you can find these on my Australia Unit pinterest board.

Vestibular Apparatus

The vestibular apparatus, is the sensory organ for detecting sensations of equilibrium.

It is encased in a system of bony tubes and chambers located in the petrous portion of the temporal bone, called the bony labyrinth.Within this system are membranous tubes and chambers called the membranous labyrinth. The membranous labyrinth is the functional part of the vestibular apparatus It is composed mainly of the cochlea (ductus cochlearis); three semicircular canals; and two large chambers, the utricle and saccule. The cochlea is the major sensory organ for hearing and has little to do with equilibrium. However, the semicircular canals, the utricle, and the saccule are all integral parts of the equilibrium mechanism.

Function of the Utricle and Saccule in the Maintenance of Static Equilibrium

It is especially important that the hair cells are all oriented in different directions in the maculae of the utricles and saccules, so that with different positions of the head, different hair cells become stimulated.The “patterns” of stimulation of the different hair cells apprise the brain of the position of the head with respect to the pull of gravity. In turn, the vestibular, cerebellar,

and reticular motor nerve systems of the brain excite appropriate postural muscles to maintain proper equilibrium.This utricle and saccule system functions extremely effectively for maintaining equilibrium when the head is in the near-vertical position. Indeed, a person

can determine as little as half a degree of dysequilibrium when the body leans from the precise upright position.

“Predictive” Function of the Semicircular Duct System in the Maintenance of Equilibrium.

Because the semicircular ducts do not detect that the body is off balance in the forward direction, in the side direction, or in the backward direction, one might ask:What is the semicircular ducts’ function in the maintenance of equilibrium? All they detect is that the person’s head is beginning

or stopping to rotate in one direction or another. Therefore, the function of the semicircular ducts is not to maintain static equilibrium or to maintain equilibrium during steady directional or rotational movements. Yet loss of function of the semicircular ducts does cause a person to have poor equilibrium when attempting to perform rapid, intricate changing body movements.

We can explain the function of the semicircular ducts best by the following illustration: If a person is running forward rapidly and then suddenly begins to turn to one side, he or she will fall off balance a fraction of a second later unless appropriate corrections are made ahead of time. But the maculae of the utricle and saccule cannot detect that he or she is off balance

until after this has occurred. The semicircular ducts,however, will have already detected that the person is turning, and this information can easily apprise the central nervous system of the fact that the person will fall off balance within the next fraction of a second or so unless some anticipatory correction is made.

In other words, the semicircular duct mechanism predicts that dysequilibrium is going to occur and thereby causes the equilibrium centers to make appropriate anticipatory preventive adjustments. In this way, the person need not fall off balance at all before he or she begins to correct the situation.

Removal of the flocculonodular lobes of the cerebellum prevents normal detection of semicircular duct signals but has less effect on detecting macular signals.

It is especially interesting that the cerebellum serves as a “predictive” organ for most rapid movements of the body, as well as for those having to do with equilibrium.

INTRODUCTION TO HUMAN ANATOMY AND PHYSIOLOGY

INTRODUCTION TO HUMAN ANATOMY AND PHYSIOLOGY

THE WORD ANATOMY IS DERIVED FROM A GREEK WORD ANATOME - TO CUT UP

a-NAT-o-me

ana = up
tomy= process of cutting

DEFINITION

Anatomy is
                        the study of structures that make up the body
                                                 &
                         how these stuctures relate with each other

It was first studied by dissection

Dissection

the careful cutting apart of body structures to study their relationships

dis-SEK-shun

dis= apart
section= act of cutting

SUB SPECIALITIES OF ANATOMY

1. GROSS ANATOMY

A. SYSTEMIC ANATOMY
B. REGIONAL ANATOMY

2. MICROSCOPIC ANATOMY

3. HISTOLOGY

4. DEVELOPMENTAL BIOLOGY

5. EMBRYOLOGY

6. SURFACE ANATOMY

7. CELLULAR ANATOMY/ CELL BIOLOGY

8. PATHOLOGICAL ANATOMY

9. RADIOGRAPHIC ANATOMY

1. GROSS ANATOMY

   - study of body structures without the use of a microscope

A. SYSTEMIC ANATOMY

                        -study of functional relationship of organs within a system

B. REGIONAL ANATOMY

-study of body parts regionally

2. MICROSCOPIC ANATOMY

-STUDY OF BODY STRUCTURES USING A MICROSCOPE

3. HISTOLOGY

-(his -TOL-o¯ -je¯; hist- tissue)

   -study of tissues

4. DEVELOPMENTAL ANATOMY

- study of the structural development of the embryo.

-Study of the complete development of an individual from fertilization of an egg to death

                           -branch of embryology

5. EMBRYOLOGY

em -bre¯-OL-o¯-je¯

embry- embryo; -logy study of

- study of the structure and development of the embryo

- Study of the first eight weeks of development ; following fertilization of an egg (in humans).
.

6. SURFACE ANATOMY

- study of the structure of the bodys surface.

-Study of Surface markings of the body to understand internal anatomy through visualization and palpation (gentle touch).

7. CELLULAR ANATOMY/ CELL BIOLOGY


- study of the structure and function of the cell.

   - a branch of cytology

CYTOLOGY-

the study of the structure, function, pathology, life cycles, and life history
of cells.

8. PATHOLOGICAL ANATOMY

(path -o¯-LOJ-i-kal; path- disease)

Study of Structural changes (from gross to microscopic) associated with disease.

9. RADIOGRAPHIC ANATOMY

ra¯-de¯-o¯-GRAF-ik

radio- ray; -graphic to write

Study of Body structures that can be visualized with x-rays.

Neoplasia Differentiation and anaplasia

Differentiation and anaplasia:
Apply to the parenchymal cells of neoplasms

Differentiation

Extent to which parenchymal cells resemble comparable normal cells, both morphologically and functionally
Well-differentiated tumors- cells resemble the mature normal cells of tissue of origin; better retains the fx of normal cells
Evolves from maturation or specialization of undifferentiated cells as they proliferate
Poorly-differentiated tumors – primitive-appearing, unspecialized cells
Does retain fx of normal cell; may acquire other fx’s such as elaboration of fetal ptns or ectopic hormone production
Derives from proliferation w/out maturation
Benign tumors usually well-differentiated
Malignant tumors usually range from anaplastic to well-differentiated

Anaplasia

Lack of differentiation
Example of anaplastic tumors = malignant neoplasms composed of undifferentiated cells
More rapidly growing and the more anaplastic a tumor, the less likely it is that there will be specialized functional activity

Morphology of Anaplasia:

Pleomorphism – variation in size and shape of both cell and nuclei
Hyperchromatic nuclei; nuclei contain an overabundance of DNA
Nuclei are too large for the cell
Nuclear to cytoplasmic ratio may reach 1:1 instead of normal 1:4 or 1:6
Chromatin is often coarsely clumped and distributed along the nuclear mbr
Usually see large nucleoli
High proliferative activity
Large numbers of mitoses
Atypical, bizarre mitotic figures sometimes w/ tripolar, quadripolar, or multipolar spindles
Tumor giant cells
Some possess only a single huge polymorphic nucleus, others w/ two or more nuclei
Loss of normal polarity; grow in sheets or large masses tumors in an anarchic, disorganized fashion
Vascular stroma is often scant; large central areas may undergo necrosis

Variations in cell growth and differentiation: normal and abnormal.

Increased growth.

Increased growth occurs in a tissue or organ due to increased functional demand. It can be the result of hyperplasia, hypertrophy or a combination of both. Stimuli for increased growth include hormones, growth factors and work against resistance.
Hyperplasia is an increase in cell number by cell division, often leading to an increase in the size of an organ.
Hypertrophy is an increase in cell size without cell division, usually leading to an increase in the size of an organ.
Both hyperplasia and hypertrophy can be physiological or pathological.

Some examples of physiological hyperplasia

The breast undergoes hyperplasia during puberty, pregnancy, and lactation, stimulated by hormones such as oestrogens, progesterone and prolactin.
Red cell precursors in the bone marrow undergo hyperplasia at high altitude, stimulated by erythropoietin, which has been evoked by hypoxia.
The thyroid undergoes hyperplasia in puberty and pregnancy, stimulated by increased metabolic demand.

Some examples of physiological hypertrophy

Skeletal muscle undergoes hypertrophy stimulated by increased muscle activity on exercise.
Cardiac muscle undergoes hypertrophy stimulated by sustained outflow increase in athletes.
Myometrium undergoes hypertrophy in pregnancy stimulated by oestrogens

Some examples of pathological hyperplasia

The prostate gland undergoes hyperplasia, stimulated by oestrogen.
The adrenal cortex undergoes hyperplasia (Cushing’s syndrome) stimulated by ACTH produced by pituitary, lung or other tumours.
The thyroid gland undergoes hyperplasia in Graves’ disease, stimulated by Thyroid-stimulating autoantibody.
The parathyroid gland undergoes hyperplasia stimulated by hypercalcaemia.
The endometrium undergoes hyperplasia stimulated by oestrogen.
Myointimal cells undergo hyperplasia in atheromatous plaques stimulated by Platelet Derived Growth Factor.
Keratinocytes in skin undergo hyperplasia in psoriasis, stimulated by cytokines released in an immune response.

Some examples of pathological hypertrophy

Cardiac muscle of the left ventricle undergoes hypertrophy because of increased outflow pressure eg systemic hypertension, aortic valve disease
Cardiac muscle of the right ventricle undergoes hypertrophy because of increased outflow pressure eg pulmonary hypertension, pulmonary valve disease.
Arterial smooth muscle undergoes hypertrophy in hypertension.
Decreased size of tissue or organ
This can occur in a tissue or organ due to developmental failure, or to reduction in size of a previously normal organ. This is atrophy.
Atrophy is a decrease in cell size and/or number in a previously normal tissue or organ. Decrease in cell number is mediated by apoptosis; decrease in cell size by a reduction in cell growth. Atrophy can be physiological or pathological.

Some examples of physiological atrophy

In the embryo & fetus, the notochord and branchial clefts undergo atrophy.
In the neonate, the umbilical vessels and ductus arteriosus undergo atrophy.
In early adulthood, the thymus undergoes atrophy.
In old age the uterus, testes, brain and bone all atrophy.

Some examples of pathological atrophy

Loss of function causes muscle atrophy and osteoporosis in immobilisation or weightlessness.
Loss of innervation causes muscle atrophy in nerve transection or poliomyelitis.
Loss of blood supply causes skin atrophy or bedsores in peripheral vascular disease or excess pressure.
Severe malnutrition causes atrophy in many tissues.
Loss of hormonal stimulation causes atrophy of adrenal cortex, thyroid, and gonads in hypopituitarism.
Excess hormones can cause atrophy: excess corticosteroids cause skin atrophy.

Abnormal differentiation
When mature tissues grow and differentiate abnormally, they can undergo metaplasia, dysplasia or both.

Metaplasia

Is defined as the transformation of one fully differentiated cell type into another.
Is an adaptive response to environmental stress, usually chronic irritation or inflammation; metaplastic tissues are better able to withstand the adverse environmental changes than are normal tissues
Is caused by activation and/or repression of groups of genes involved in the maintenance of cellular differentiation
There is no intrinsic gene defect (as there is in neoplasia), therefore metaplasia is reversible.
But, metaplastic tissues are more genetically unstable than their normal counterparts, so they may undergo further transformation to dysplasia and neoplasia
Can affect epithelial or connective tissue cells

Epithelial metaplasia can be:

Squamous: other epithelia transform to squamous epithelium.
Glandular: other epithelia transform to glandular epithelium.

Some examples of Squamous metaplasia are:

Ciliated pseudostratified columnar epithelium of respiratory tract; due to smoking, bronchiectasis, or chronic bronchitis.
Simple columnar epithelium of endocervix; due to changes of pH, injury, inflammation.
Transitional cell epithelium of bladder; due to Schistosomal infection or bladder calculi.

Some examples of Glandular metaplasia are:

Stratified squamous epithelium of oesophagus transforms to simple columnar epithelium due to gastro-oesophageal reflux: Barrett’s oesophagus.
Simple columnar epithelium of stomach transforms to intestinal epithelium, in chronic gastritis due to Helicobacter pylori

Mesenchymal metaplasia is much less common than epithelial metaplasia. There are three main types:

Osseous metaplasia – in old scars such as tuberculous scars in the lungs, in atheromatous plaques and in chronically damaged muscle
Chondroid metaplasia – in similar conditions to osseous metaplasia
Myeloid metaplasia (also known as extramedullary haemopoiesis) – in the spleen, liver and lymph nodes in patients with myeloproliferative diseases

Dysplasia refers to cells of abnormal phenotype that are not yet neoplastic, but are predisposed to be.

Encountered primarily in the epitheli
It is a premalignant process.
It is often preceded by metaplasia.
It is usually irreversible.
There is disordered maturation: the phenotype of the abnormal cells approaches that of malignant cells. Loss in uniformity of the individual cells as well as a loss in their architectural orientation. It is characterised by increased cell division, atypical cell morphology and lack of differentiation.
Considerable architectural anarchy
Considerable pleomorphism
Hyperchromatic nuclei
Nuclei are too large for cell
Increase numbers of mitotic figures, but conform to normal patterns; may appear in abnormal location w/in the epithelium

Examples include:

in str sq epithelium, mitoses are not confined to basal layers, may occur in surface cells.
Colonic epithelial dysplasia in longstanding ulcerative colitis.
Cervical Intraepithelial Neoplasia (CIN).
Glandular dysplasia in Barrett’s oesophagus
Paget’s disease of bone.

Carcinoma in situ

When dysplastic changes are marked and involve the entire thickness of the epithelium
Epithelial dysplasia almost invariably comes before the appearance of cancer
Dysplasia does not necessarily progress to cancer.

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