Cell Biology

Cell biology or cytology is a branch of biology that deals with studies related to the structure and function of a cell-based on the concept that the cell is the fundamental unit of life.

• A detailed study of the cellular structure and function provides a basis for studies related to tissues, organs, and the body.
• The number of cells in an organism might differ as some organisms have a single cell while others are made up of billions of cells.
• In the case of single-celled organisms, the singular cell is studied, whereas, for multicellular organisms, individual cells of different tissues are studied.
• Initially, only the outer structure of a cell was studied due to the lack of complex microscopic processes.
• Over the years, however, advancements in other areas have made it possible to study the internal cellular components of a cell.
• Apart from the cell structure and function, cell biology also deals with cell communication and signaling.
• Cell biology also involves the studying of the cell cycle and cell division, which provides insight into the cellular composition of an organism.
• Cell biology is also linked with other studies like genetics, molecular biology, cytochemistry, and biochemistry.
• Cells are distinguished as prokaryotic and eukaryotic cells based on the complexity of the cell.
• Cell biology enables studying the biochemical mechanisms involved in cell metabolism and different forms of cellular energy.
• Focusing on the structural and functional aspects of a single cell allows a detailed understanding of the body overall.
• It is also easier to perform research on a single cell as it can be modified and observed efficiently.
• Techniques in cell biology have advanced over the years with new and improved imaging techniques to observe smaller cellular organelles.
• Cell biology, together with systemic biology, helps in the answering of complex questions like the relationship between cellular networks, the evolutionary relationship between genomes, and the complexity of the biomolecular composition of different living organisms.

Definition of animal cell

An animal cell is a eukaryotic cell that lacks a cell wall, and it is enclosed by the plasma membrane. The cell organelles are enclosed by the plasma membrane including the cell nucleus. Unlike the animal cell lacking the cell wall, plant cells have a cell wall.

Animals are a large group of diverse living organisms that make up three-quarters of all species on earth. With their ability to move, respond to stimuli, respond to environmental changes, and adapt to different modes of feeding defense mechanisms and reproduction, all these mechanisms are enhanced by their constituent elements in the body. However, animals cannot manufacture their own food like plants and hence they depend on plants in one way or another.

All living things are made up of cells that make up their body structure. Some of these living things are single-celled (unicellular) and other organisms are made up of more than one cell (Multicellular).

A cell is the smallest (microscopic) structural-functional unit of life of an organism. The cells that constitute an animal are called Animal cells and those that constitute plants are known as plant cells.

Most cells are covered by a protective membrane known as the cell wall which gives the cells their shape and rigidity.

Since animal cells lack a rigid cell wall it allows them to develop a great diversity of cell types, tissues, and organs. The nerves and muscles are made up of specialized cells that plant cells cannot evolve to form, hence giving these nerve and muscle cells have the ability to move.

Animal cell size and shape

Animal cells come in all kinds of shapes and sizes, with their size ranging from a few millimeters to micrometers. The largest animal cell is the ostrich egg which has a 5-inch diameter, weighing about 1.2-1.4 kg and the smallest animal cells are neurons of about 100 microns in diameter.

Animal cells are smaller than the plant cells and they are generally irregular in shape taking various forms of shapes, due to lack of the cell wall. Some cells are round, oval, flattened or rod-shaped, spherical, concave, rectangular. This is due to the lack of a cell wall. Note: most of the cells are microscopic hence they can only be seen under a microscope in order to study their anatomy.

But animal cells share other cellular organelles with plant cells as both have evolved from eukaryotic cells.

As noted earlier, animal cells are eukaryotic cells with a membrane-bound nucleus. therefore they have their genetic material in the form of DNA enclosed in the nucleus. They also have several structural organelles within the plasma membrane which perform various specific functions for proper cell function and generally to maintain the body normal mechanisms.

List of Animal cell organelles

Plasma membrane (Cell membrane)

Nucleus

Cytoplasm

Mitochondria

Ribosomes

Endoplasmic Reticulum (ER)

Golgi apparatus (Golgi bodies/Golgi complex)

Lysosomes

Cytoskeleton

Microtubules

Centrioles

Peroxisomes

Cilia and Flagella

Endosome

Vacuoles

Microvilli

Medical Female Infertility

 A common condition, female infertility is an inability to get pregnant and have a successful pregnancy. This is typically diagnosed after a woman has tried to get pregnant (through unprotected sex) for 12 months without a pregnancy. There are many treatment options for infertility, including medications to correct hormonal issues, surgery for physical problems and in vitro fertilization (IVF).

What is female infertility?

Infertility is a disease in which the ability to get pregnant and give birth to a child is impaired or limited in some way. For heterosexual couples (man and woman), this is usually diagnosed after one year of trying to get pregnant (but may be diagnosed sooner depending on other factors). For heterosexual couples, one third of causes of infertility are due to a male problem, one third are due to a female problems, and one third are due to combination or unknown reasons. When the cause of the infertility is found to come from the female partner, it’s considered female infertility or “female factor” infertility.

How common is female infertility?

Infertility is a common disease. At least 10% of women deal with infertility of some kind. The chances of being infertile increases as a woman ages.

SYMPTOMS AND CAUSES

What causes female infertility?

There are many possible causes of infertility. However, it can be difficult to pinpoint the exact cause, and some couples have “unexplained” infertility or “multifactorial” infertility (multiple causes, often both male and female factors). Some possible causes of female factor infertility can include:

Problems with the uterus: This includes polyps, fibroids, septum or adhesions inside the cavity of the uterus. Polyps and fibroids can form on their own at any time, whereas other abnormalities (like a septum) are present at birth. Adhesions can form after a surgery like a dilation and curettage (D&C).

Problems with the fallopian tubes: The most common cause of “tubal factor” infertility is pelvic inflammatory disease, usually caused by chlamydia and gonorrhea.

Problems with ovulation: There are many reasons why a woman may not ovulate (release an egg) regularly. Hormonal imbalances, a past eating disorder, substance abuse, thyroid conditions, severe stress and pituitary tumors are all examples of things that can affect ovulation.

Problems with egg number and quality: Women are born with all the eggs they will ever have, and this supply can “run out” early before menopause. In addition, some eggs will have the wrong number of chromosomes and cannot fertilize or grow into a healthy fetus. Some of these chromosomal issues (such as “balanced translocation”) may affect all of the eggs. Others are random but become more common as a woman gets older.

Who is at risk for female infertility?

Many factors can increase a woman’s risk of female infertility. General health conditions, genetic (inherited) traits, lifestyle choices and age can all contribute to female infertility. Specific factors can include:

Age.

Hormone issue that prevents ovulation.

Abnormal menstrual cycle.

Obesity.

Being underweight.

Having a low body-fat content from extreme exercise.

Endometriosis.

Structural problems (problems with the fallopian tubes, uterus or ovaries).

Uterine fibroids.

Cysts.

Tumors.

Autoimmune disorders (lupus, rheumatoid arthritis, Hashimoto’s disease, thyroid gland conditions).

Sexually transmitted infections (STIs).

Polycystic Ovary Syndrome (PCOS).

Primary Ovary Insufficiency (POI).

Excessive substance use (heavy drinking).

Smoking.

DES syndrome (DES is a medication that was given to women to prevent complications in pregnancy like premature birth or miscarriage. However, this medication has caused infertility in some of the children of mothers who took DES.).

A past ectopic (tubal) pregnancy.

How does age impact female infertility?

As a woman ages, her chances of becoming pregnant decreases. Age is becoming a more common factor in female infertility because many couples are waiting to have children until their 30s or 40s. Women over age 35 have a higher risk of having fertility issues. The reasons for this include:

Overall number of eggs is lower.

More eggs have an abnormal number of chromosomes.

An increased risk of other health conditions.

What will my doctor ask during an appointment to diagnose female infertility?

Your healthcare provider will need to know about your menstrual periods, any past pregnancies, miscarriages, pelvic pain, unusual vaginal bleeding or discharge. You may also be asked about any past pelvic infections or sexually transmitted infections (STIs). Some questions may include:

Have you had any previous pregnancies or miscarriages?

Is your menstrual cycle normal and regular or painful and irregular?

Do you have heavy bleeding or abnormal discharge?

Do you have any pelvic pain?

Have you had any abdominal surgeries in the past?

What tests will my healthcare provider run to diagnose female infertility?

Some tests may be done in your healthcare provider’s office as a physical exam. These tests may include:

An overall physical exam.

A Pap test.

A pelvic exam.

A pelvic ultrasound.

An examination of the breasts for unusual milk production.

Other tests may need to be done in a lab. These tests can include:

Blood tests: The type of lab tests will depend on your health history and what diagnoses your doctor is considering. Examples of lab tests include thyroid testing, prolactin levels, tests of ovarian reserve and progesterone (a hormone produced during the menstrual cycle that signals ovulation).

X-ray hysterosalpingogram (HSG): A dye is injected into the cervix and the caregiver watches how the dye moves through the fallopian tube with an X-ray. This test checks for blockages.

Laparoscopy: In this test, a small monitoring instrument called a laparoscope is inserted into the abdomen to look at the organs.

Transvaginal ultrasound: Unlike an abdominal ultrasound (where the probe is placed over the belly), this test is done by inserting an ultrasound wand into the vagina. It allows the healthcare provider a better view of organs like the uterus and ovaries.

Saline sonohysterogram (SIS): This test is used to look at the lining of the uterus and assess for polyps, fibroids or other structural abnormalities. Saline (water) is used to fill the uterus, allowing the healthcare provider to get a better view of the uterine cavity during a transvaginal ultrasound.

Hysteroscopy: In this test, a device called a hysteroscope (a flexible, thin device with a camera on it) is inserted into the vagina and through the cervix. The healthcare provider moves it into the uterus to view the inside of the organ.

MANAGEMENT AND TREATMENT

How is female infertility treated?

Once your healthcare provider has diagnosed female infertility and pinpointed the cause, there are a variety of treatment options. The cause of the infertility guides the type of treatment. For example, structural problems may be treated through surgery, while hormonal medications can be used for other issues (ovulation issues, thyroid conditions).

Many patients will require artificial insemination (injecting washed sperm into the uterus after ovulation) or in vitro fertilization (fertilizing eggs with sperm in the lab to make embryos, then transferring the embryo into the uterus).

Adoption and gestational surrogacy may also be options for women with infertility who wish to start a family.

PREVENTION

Can female infertility be prevented?

Most forms of female infertility cannot be predicted or prevented. However, the risk factors that may contribute to infertility can, in some cases, be controlled to prevent this condition. For example, lifestyle modifications, such as reducing alcohol consumption and quitting smoking, may be beneficial to one’s fertility, as is maintaining a healthy weight and developing good exercise habits. It’s important to regularly visit your healthcare provider and discuss any other risks you may have for female infertility.

OUTLOOK / PROGNOSIS

What is the outlook for female infertility?

The outlook (prognosis) for female infertility depends greatly on the individual and the underlying cause of infertility. In cases where medication can be used to treat an ovulatory condition, or a simple surgical procedure can be used to correct a structural abnormality (polyps or solitary fibroids), the outlook is generally positive. Talk to your doctor about your family history, risk factors and underlying medical issues to learn more about your prognosis.

LIVING WITH

When should I see my doctor about female infertility?

If you are a woman in a heterosexual relationship with regular intercourse and menstrual cycles, you should see your doctor after 12 months of trying to conceive (become pregnant) without using birth control (six months if you are over the age of 35). It’s also important to regularly visit your healthcare provider once you become sexually active.

A note from Cleveland Clinic

Infertility can be incredibly stressful. If you have been trying to get pregnant for 12 months without success — or six months if you are over the age of 35 — reach out to your healthcare provider. Once you are diagnosed, your provider can help you develop a plan moving forward