Cell Adaptations : Pathology - Hypertrophy, Hyperplasia, Atrophy & Metaplasia

Summary

The video explains the concept of cell adaptations, highlighting four main types: hypertrophy, hyperplasia, atrophy, and metaplasia. Hypertrophy involves an increase in cell size, often due to increased workload or hormonal stimulation. Hyperplasia refers to an increase in cell number, either as a physiological response or due to excess hormones. Atrophy is the decrease in cell size or number, often linked to aging or disease. Metaplasia involves the transformation of one differentiated cell type into another, often in response to chronic irritation. The video delves into each adaptation's mechanisms, causes, and examples, providing a comprehensive understanding of cellular responses.

Takeaways

• 😀 Hypertrophy refers to the increase in cell size, leading to organ enlargement, driven by increased workload or hormonal stimulation.
• 😀 Hypertrophy can be physiological, as in muscle growth due to exercise, or pathological, such as cardiac hypertrophy due to long-term hypertension.
• 😀 Cells capable of division can undergo both hypertrophy and hyperplasia, but non-dividing cells, like myocardial cells, only experience hypertrophy.
• 😀 Hyperplasia is the increase in the number of cells in a tissue or organ, which can be physiological (e.g., breast tissue during pregnancy) or pathological (e.g., benign prostatic hyperplasia).
• 😀 Atrophy refers to the decrease in organ size, either due to a reduction in cell size (physiological or pathological) or cell number (e.g., in starvation or inflammation).
• 😀 Physiological atrophy is common during development (e.g., in fetal structures like the ductus arteriosus) and post-pregnancy (e.g., in the uterus and breasts).
• 😀 Pathological atrophy may result from starvation, hormonal changes (e.g., hypopituitarism), or prolonged disuse, such as immobilization due to a fracture.
• 😀 The mechanism of atrophy involves decreased protein synthesis and increased protein degradation, with pathways like the ubiquitin-proteasome system and autophagy playing key roles.
• 😀 Metaplasia is the reversible transformation of one differentiated cell type into another, often due to chronic environmental stress, such as squamous metaplasia in the respiratory tract from smoking.
• 😀 Although metaplasia helps cells adapt, it can impair organ function and, if prolonged, may lead to malignant transformation of the metaplastic cells.

Q & A

What are cell adaptations and why are they important?

Cell adaptations are reversible changes in the size, number, phenotype, metabolic activity, or functions of cells in response to changes in their environment. These adaptations are important as they allow cells to adjust to stress or altered conditions to maintain homeostasis.

What is hypertrophy and how does it occur?

Hypertrophy refers to an increase in the size of cells, which leads to an increase in the size of the organ. It occurs when cells experience increased demand for their function, or due to hormonal or growth factor stimulation. In hypertrophy, the cell size increases through the synthesis of more structural components, but no new cells are formed.

What is the difference between physiological and pathological hypertrophy?

Physiological hypertrophy occurs in response to normal stimuli, like muscle enlargement in bodybuilders or uterine growth during pregnancy. Pathological hypertrophy, on the other hand, results from abnormal stress, such as in the heart due to long-term hypertension or valve issues.

Can hypertrophy and hyperplasia occur together?

Yes, hypertrophy and hyperplasia can coexist. When both processes happen together, the size of the organ increases due to both an increase in cell size (hypertrophy) and an increase in cell number (hyperplasia).

What is hyperplasia and how does it differ from hypertrophy?

Hyperplasia is an increase in the number of cells in an organ or tissue, which generally leads to an increase in its size. Unlike hypertrophy, which involves an increase in cell size, hyperplasia involves cell division and an increase in cell numbers.

What are the types of hyperplasia?

There are two main types of hyperplasia: hormonal hyperplasia, which increases the functional capacity of an organ (e.g., breast tissue during pregnancy), and compensatory hyperplasia, which increases tissue mass after damage or partial resection (e.g., liver regeneration after hepatectomy).

What is atrophy and what causes it?

Atrophy is the reduction in the size of an organ or tissue due to a decrease in cell size and number. It can be caused by factors such as malnutrition, aging, lack of hormonal stimulation, or reduced blood supply.

How does disuse atrophy occur and what are its effects?

Disuse atrophy occurs when a muscle is immobilized or a person is confined to bed rest, leading to the loss of muscle mass. The initial decrease in muscle size is reversible, but prolonged disuse leads to permanent muscle fiber loss due to apoptosis.

What is metaplasia and when does it occur?

Metaplasia is the replacement of one differentiated cell type with another. It commonly occurs in epithelial and connective tissues as a response to stress or injury. For example, squamous metaplasia occurs in the respiratory tract due to chronic irritation like cigarette smoke.

How does metaplasia relate to cancer risk?

Although metaplasia is an adaptive response that helps cells survive environmental changes, persistent metaplasia can lead to the loss of normal cell functions and may increase the risk of malignant transformation, eventually leading to cancer.