Histology: Adipose Tissue

Questions and Answers

What role does leptin play in the body?

It regulates appetite and influences the formation of adipose tissue. (correct)

It increases the storage of triglycerides.

It acts as a primary energy source for muscle cells.

It facilitates the conversion of glucose into fatty acids.

Which substance stimulates the cyclic AMP (cAMP) system in adipocytes?

Insulin

Norepinephrine (correct)

Glucose

Glycerol phosphate

What is the primary function of hormone-sensitive lipase?

To regulate glucose uptake in muscle cells.

To synthesize glycerol phosphate from glucose.

To hydrolyze stored triglycerides into free fatty acids. (correct)

To transport triglycerides in lipoprotein complexes.

What are chylomicrons primarily responsible for transporting?

Triglycerides from the intestine and liver. Signup and view all the answers

Which of the following is NOT a component involved in triglyceride metabolism?

Albumin transporting glycerol Signup and view all the answers

In the context of lipid mobilization, what does cAMP activate?

Hormone-sensitive lipase. Signup and view all the answers

What is the result of the action of hormone-sensitive lipase on triglycerides?

Triglycerides are hydrolyzed into free fatty acids and glycerol. Signup and view all the answers

What type of lipoprotein is responsible for transporting triglycerides to tissues?

VLDL Signup and view all the answers

What is the primary function of brown adipocytes?

Release heat to warm the blood Signup and view all the answers

What distinguishes brown adipose tissue from white adipose tissue?

Greater vascularization and mitochondria Signup and view all the answers

What percentage of body weight does adipose tissue typically represent in women?

15%-20% Signup and view all the answers

How does adipose tissue contribute to energy metabolism?

By storing triglycerides and releasing them when needed Signup and view all the answers

What unique structural feature do adipocytes possess compared to other connective tissue cells?

A thin external lamina containing type IV collagen Signup and view all the answers

What health issues are associated with the functions of adipocytes and adipose tissue?

Obesity, diabetes, and heart disease Signup and view all the answers

Which statement is TRUE about the histogenesis of adipose tissue?

Both brown and white adipose tissues form mainly through mesenchymal stem cells. Signup and view all the answers

What role does vascularization play in adipose tissue?

It facilitates the transport of oxygen and nutrients to adipocytes. Signup and view all the answers

What role do fatty acids play once they diffuse into the capillary?

They bind with albumin for transport. Signup and view all the answers

What happens to free fatty acids in the adipocyte?

They are reesterified to glycerol phosphate. Signup and view all the answers

How does the presence of visceral adipose tissue affect health risks?

It raises the risk of diabetes and cardiovascular disease. Signup and view all the answers

Why might leptin treatment not be effective for obese humans?

Obese individuals have defective receptors for leptin. Signup and view all the answers

What differentiates visceral fat from subcutaneous fat in a medical context?

Visceral fat affects metabolic health more negatively than subcutaneous fat. Signup and view all the answers

What is the primary composition of triglycerides formed in adipocytes?

Glycerol and fatty acids. Signup and view all the answers

Which of the following is a characteristic of white adipose tissue?

It helps in energy storage and insulation. Signup and view all the answers

What are the potential consequences of elevated levels of leptin in humans?

Resistance to the effects of leptin itself. Signup and view all the answers

What is the primary function of brown adipocytes in lipid metabolism?

To release heat instead of ATP Signup and view all the answers

Which process describes beige adipocytes changing in response to cold temperatures?

They reversibly change to resemble brown adipocytes. Signup and view all the answers

At what stage of development do humans begin to accumulate white adipose tissue?

By the 14th week of gestation Signup and view all the answers

What is the role of white adipose tissue in the body?

To store energy and secrete various cytokines Signup and view all the answers

What characterizes the state of adipose tissue in obesity?

A state of chronic mild inflammation Signup and view all the answers

What primarily contributes to adult-onset obesity?

The hypertrophy of existing adipocytes Signup and view all the answers

What is a significant factor in the regulation of adipocyte differentiation?

Proliferation of mesenchymal stem cells Signup and view all the answers

What primarily drives excessive adipose tissue accumulation leading to obesity?

Nutritional intake exceeding energy expenditure Signup and view all the answers

What role does nor-epinephrine play in brown adipose tissue during hibernation?

It activates hormone-sensitive lipase in adipocytes. Signup and view all the answers

How does the thermogenic activity of brown adipocytes compare to other cells?

It is greater than that of other cells. Signup and view all the answers

What happens to the amount of brown fat in humans from birth to adulthood?

It peaks at birth and then decreases. Signup and view all the answers

Which unique characteristic distinguishes multilocular adipocytes from unilocular ones?

They have higher levels of uncoupling protein-1. Signup and view all the answers

What is the function of uncoupling protein-1 (UCP1) in brown adipose tissue?

It allows protons to flow, increasing heat production. Signup and view all the answers

What triggers the increase in the number of brown adipocytes during cold adaptation?

A reversible shift of beige cells to functional brown cells. Signup and view all the answers

What is the result of brown adipocyte differentiation being stimulated by autonomic nerves?

Increased differentiation and reduced apoptosis. Signup and view all the answers

During what developmental stage does brown adipose tissue typically emerge in humans?

At birth. Signup and view all the answers

Study Notes

White Adipose Tissue

Adipose tissue predominantly consists of adipocytes, specialized for fat storage, typically found isolated or in small groups within connective tissue.
Represents 15%-20% of body weight in men and slightly more in women.
Functions include lipid storage (primarily triglycerides) and regulation of energy metabolism.
Adipocytes are surrounded by a thin external lamina containing type IV collagen, distinguishing them from other connective tissue cells.
Leptin, a hormone produced by adipocytes, regulates appetite and is linked to obesity-related health issues like diabetes and heart disease.

Brown Adipose Tissue

Brown adipose tissue is characterized by multiple lipid droplets and abundantly present mitochondria, giving it a darker appearance.
Primarily functions in thermogenesis by releasing heat, particularly important in newborns and during cold adaptation.
Mitochondria of brown adipocytes significantly contribute to heat generation rather than ATP production.
Norepinephrine activates hormone-sensitive lipase, facilitating the hydrolysis of triglycerides into fatty acids and glycerol; this supports energy expenditure.

Lipid Storage and Mobilization

Triglycerides are transported via lipoprotein complexes (chylomicrons and VLDLs) from the intestine and liver.
Lipoprotein lipase in capillaries partially breaks down these complexes, allowing free fatty acids and glycerol to diffuse into adipocytes for storage.
Stored triglycerides can be reesterified to glycerol phosphate and held in lipid droplets until energy is needed.

Differences Between White and Brown Fat

White adipose tissue is associated with varying medical risks; visceral fat (belly fat) is linked to higher risks of diabetes and cardiovascular issues, while subcutaneous fat is less harmful.
Beige adipocytes can transform into brown adipocytes in response to cold temperatures, enhancing heat production.
Adult-onset obesity typically involves adipocyte hypertrophy rather than an increase in the number of fat cells.

Development and Regulation

White adipose tissue develops in utero and is fully formed by the 14th week of gestation; both visceral and subcutaneous fat are present at birth.
New adipocyte formation occurs mainly during adolescence from mesenchymal stem cells around small blood vessels.
Chronic mild inflammation is characteristic of obesity due to proinflammatory cytokines released from excess visceral fat.

Thermogenic Response

Cold exposure stimulates the differentiation of beige cells into brown adipocytes, leading to increased thermogenesis and metabolic activity.
UCP1 (thermogenin) facilitates proton flow in mitochondria, enhancing heat production in response to free fatty acids.
The number of brown adipocytes increases through cold adaptation and may also involve proliferation and differentiation of progenitor cells.

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Description

Explore the fascinating aspects of adipose tissue, focusing on white and brown adipocytes. This chapter delves into the histogenesis and functions of these critical cells in the human body. Test your knowledge on the characteristics and roles of adipose tissue.