As we have seen, cells and cell structures share a number of similarities, and the same applies to the longevity of a cell. We conclude this overview of cytology with an explanation that defines the two main types of ‘death’ experienced by cells.
Cellular necrosis and apoptosis
Necrosis defines cellular death caused by unexpected damage to the cell that can be caused by a number of sources:
•Exposure to toxic chemicals
•Trauma
•Blocked blood flow
•Radiation
In such cases, the cell literally ruptures or pops like an overfilled water balloon, allowing the interior components of the cell to disperse into the cellular environment. Once there, the remnants are consumed by phagocytes.
Figure 2-17 Cellular necrosis
Apoptosis is ‘normal’ cellular death; think of it as an aging cell that eventually wears out. The cell begins to lose its structural shape and further breaks down into smaller bodies.
Some studies have explored the potential of some vaccines to trigger apoptosis in mouse livers.12 Studies attempting to determine whether some cytotoxic anti-cancer agents actually trigger and influence apoptosis have been performed since 2000,13 resulting in improved cancer treatments.
The National Cancer Institute has developed apoptosis inducers,14 which actually cause cancer cells to succumb to apoptosis. Cancer cells have the unique ability to resist apoptosis, but angiogenesis inhibitors and delivery of monoclonal antibodies15 that dispense toxic molecules into cancer cells has shown positive progress in the treatment of different types of cancers today.
Apoptosis is often called a programmed cellular death and is natural. Apoptosis does not cause a cell to ‘burst’ as with necrosis, but rather allows the cell to be consumed and eventually removed.
■Conclusion
Cells are incredibly complex; responsible for hundreds of functions in the human body. Cells are the foundation of any structure in the body and vary in size, shape, and function. Each performs a specific job in the human body.
Cytology provides a fascinating glimpse into the smallest units of life; without which there would be no life. Cells provide the foundation of all living things, from simple amoebas to people, animals, and plants. It is estimated that the human body contains multiple trillions of cells, all with predestined functions and activities that sustain life for decades.
Case Study Conclusion
Dr. Sanderson has sent Erica’s biopsy to the pathology lab. He is aware that melanoma is rated as the fifth most common cancer for men and the seventh most common malignancy found in women.16 The American Cancer Society estimates approximately 87,000 new cases of melanoma will be diagnosed in 2017.17 He hopes that Erica has come to him early enough to enjoy many years to come. He received the biopsy results and his suspicions of a cutaneous melanoma were verified. He had been careful to note the classification and thickness of the suspected cutaneous melanoma (T1, less than or equal to 1.0, and without ulceration and mitosis less than 1/millimeter2.)
After discussing the results with Erica, he scheduled a procedure to remove the melanoma. He then recommended that she undergo annual skin examinations on a yearly basis and be proactive with her own monthly skin examinations. He also showed her how to perform a self-lymph node exam, recommended for patients with stage IA cutaneous melanoma, which was Dr. Sanderson’s determination. He also recommended she undergo physical examinations with special focus on her skin and lymph nodes every three to 12 months for the next five years and then on an annual basis as indicated. Routine imaging was not recommended.
He stressed to her the importance of these follow-ups to identify any recurrence early on, as patients diagnosed with any stage of melanoma have an up to 8% risk over lifetime of developing a secondary primary melanoma.
■Questions
1.What does selective permeability imply in regard to the plasma membrane?
A.It serves as an impassable protective barrier.
B.It allows movement of only lipids.
C.It allows certain substances to enter or leave the cell while preventing others from doing so.
D.It’s a membrane that is not composed of a phospholipid bilayer.
Answer: C. The cell membrane is permeable, which enables certain substances to enter or exit, depending on function.
Learning Objective: 1
2.Which organelle is responsible for the formation of the mitotic spindle and is also involved in mitosis as well as regulation of the cell cycle?
A.Mitochondria
B.Centrosomes
C.Cytoskeleton
D.Peroxisomes
Answer: B. Centrosomes are involved in several vital functions of the many organelles in the cell found inside the cellular matrix. The centrosomal matrix organizes development of the mitotic spindle and microtubule generation in cell division.
Learning Objective: 2
3.Which type of transport is the most common and how does it work?
A.Active. Active transport processes cannot cross the cellular membrane.
B.Passive. Passive transport implies a process where molecules move from areas of high molecule concentration to areas of lower concentrations.
C.Active. Describing a unique process where one-half of a protein molecule is embedded into the inside of a molecule and the other half protrudes to the outside of the cell membrane.
D.Passive. Describes a situation where ion molecules move from areas of low concentration to areas of high concentration.
Answer: C. Active transport is the most common form of transport and defines the movement of molecules across the cell membrane facilitated by the energy supplied by ATP. This energy is needed for transportation.
Learning Objective: 3
4.Which type of cancers are most commonly diagnosed in younger people than older people?
A.Sarcomas
B.Carcinomas
C.Non-Hodgkin’s lymphoma
d.Bone cancer
Answer: C. Carcinomas such as skin cancer, lung cancer, and colon cancer are more prevalently diagnosed in younger individuals than older. In some cases, these types of cancers may be a result of lifestyle (smoking, diet, drug use, overexposure to sunlight, environmental factors, etc.)
Learning Objective: 5
■References
| 1. |
Science of Aging [Internet] “Robert Hooke and The Discovery of the Cell”, accessed April 2017. Available from
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