CHAPTER 6: ADIPOSE TISSUE Flashcards by Burn Franza

Connective tissue in which fat-storing cells or adipocytes.

typically found isolated or in small groups within loose or dense irregular connective tissue

Adipose Tissue

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normally represents 15%-20% of the body weight in men, somewhat more in women.

Adipose Tissue

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serving as storage depots for neutral fats, chiefly triglycerides (long-chain fatty acyl esters of glycerol), adipocytes function as key regulators of the body’s overall energy metabolism.

Adipose Tissue

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(long-chain fatty acyl esters of glycerol)

triglycerides

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specialize in concentrating triglycerides as lipid droplet(s), with other cells normally accumulating relatively little lipid.

Adipocytes

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active cells metabolically, responding to both nervous and hormonal stimuli. They release hormones and various other important substances.

Adipocytes

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Dominate connective tissue o found isolated or in small groups within loose or dense irregular connective tissue o active cells metabolically, responding to both nervous and hormonal stimuli. o release hormones and various other important substances and adipose tissue is now recognized as an endocrine organ at the center of nutritional homeostasis.

Adipocytes

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2 TYPES OF TISSUE

White Adipose Tissue
Brown Adipose Tissue

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common type specialized for fat storage, consists of cells each containing one large cytoplasmic droplet of whitish-yellow fat.

White Adipose Tissue

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contains cells with multiple lipid droplets interspersed among abundant mitochondria, which helps give this tissue a darker appearance.

Brown adipose tissue

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release heat and function to warm the blood.

Brown adipose tissue

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Specialized for relatively long-term energy storage, adipocytes of white adipose tissue are spherical when isolated but are polyhedral when closely packed in situ.

WHITE ADIPOSE TISSUE

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When completely developed, a white adipocyte is very large, between 50 and 150 μm in diameter, and contains a single huge droplet of lipid filling almost the entire cell.

WHITE ADIPOSE TISSUE

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the single large droplet of triglycerides, white adipocytes are also called unilocular

White Adipocytes

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the lipid is removed from cells by _____

XYLENE

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adipocytes are often empty in standard light microscopy

UNILOCULAR

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have a signet-ring appearance, with the lipid droplet displacing and flattening the nucleus against the cell membrane

White Adipocytes

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produces hormone called _____ or “satiety factor” with target cells in the hypothalamus, o can store triglycerides

LEPTIN

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triglycerides derived from three sources:

Dietary fats brought to the cells via the circulation as chylomicrons
Lipids synthesized in the liver and transported in blood with very low-density lipoproteins (VLDLs)
Free fatty acids and glycerol synthesized by the adipocytes.

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generate benign tumors called lipomas that are relatively common, although malignant adipose tumors (liposarcomas) occur infrequently. Fetal lipomas of brown fat are sometimes called hibernomas.

Unilocar Adipocytes

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generate benign tumors called ____

lipomas

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malignant adipose tumors

liposarcomas

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Fetal lipomas of brown fat are sometimes called ___

HIBERNOMAS

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Most _________ in a white adipocyte are near the peripheral nucleus, including mitochondria, a small Golgi apparatus, a few cisternae of RER, and free polyribosomes.

cytoplasmic organelles

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peripheral nucleus, including ______

mitochondria, a small Golgi apparatus

The thin, submembranous layer of cytoplasm surrounding the lipid droplet contains ________________

cisternae of smooth ER (SER) and pinocytotic vesicles.

form a fine interwoven network that supports individual fat cells and binds them together

Reticular fibers

between adipocytes may not always be apparent in tissue sections.

microvasculature

The distribution of _____________ changes significantly through childhood and adult life and is partly regulated by sex hormones controlling adipose deposition in the breasts and thighs.

white adipose tissue

( (Gr. chylos, juice + micros, small) are particles of variable size, up to 1200 nm in diameter.

Chylomicrons

formed from ingested lipids in epithelial cells lining the small intestine and transported in the blood and lymph.

Chylomicrons

They consist of a core containing mainly triglycerides, surrounded by a stabilizing monolayer of phospholipids, cholesterol, and several apolipoproteins.

Chylomicrons

Very Low Density Lipoprotein (VLDL)

smaller complexes (30-80 nm, providing a greater surface-to-volume ratio), of similar lipid and protein composition to chylomicrons, but are synthesized from lipids in liver cells.

Very Low Density Lipoprotein (VLDL)

In adipose tissue both _____________ are hydrolyzed at the luminal surfaces of blood capillaries by lipoprotein lipase, an enzyme synthesized by the adipocytes and transferred to the capillary cell membrane.

chylomicrons and VLDLs

Levels of circulating lipoproteins are routinely measured in clinical tests for blood lipids, after fasting to allow depletion of chylomicrons. Varying levels of apoproteins and triglycerides in the complexes allow their categorization according to density, from VLDL to high-density lipoprotein (HDL).

Very Low Density Lipoprotein (VLDL)

stimulates glucose uptake by adipocytes and accelerates its conversion into triglycerides, and the production of lipoprotein lipase.

Insulin

released in the adrenal gland and by postganglionic sympathetic nerves in adipose tissue activates a hormone-sensitive lipase that breaks down triglycerides at the surface of the stored lipid droplets.

Norepinephrine

Scientific name for LEPTIN

16KDA polypeptide hormone

a “satiety factor” with target cells in the hypothalamus, other brain regions, and peripheral organs, which helps regulate the appetite under normal conditions and participates in regulating the formation of new adipose tissue.

LEPTIN

are transported by blood and lymph from the intestine and liver in lipoprotein complexes known as chylomicrons (Chylo) and VLDLs.

Triglycerides

In the capillary endothelial cells of adipose tissue, these complexes are partly broken down by _____________, releasing free fatty acids and glycerol. The free fatty acids diffuse from the capillary into the adipocyte, where they are reesterified to glycerol phosphate, forming triglycerides that are stored in the lipid droplet until needed.

lipoprotein lipase

stimulates the cyclic AMP (cAMP) system, which activates hormone-sensitive lipase to hydrolyze the stored triglycerides to free fatty acids and glycerol.

Norepinephrine

Although______________ associated with different organs appears histologically similar, differences in gene expression have been noted between visceral deposits (in the abdomen) and subcutaneous deposits of white fat. Such differences may be important in the medical risks of obesity; it is well established that increased visceral adipose tissue raises the risk of diabetes and cardiovascular disease, whereas increased subcutaneous fat does not.

white adipose tissue

differentiate as progenitor cells for all types of connective tissue, including preadipocytes.

Mesenchymal stem cells

developing within the lateral mesoderm of the embryo produce large number of white adipocytes (forming white adipose tissue) and a smaller number of so-called beige adipocytes with cytological features and gene expression patterns of both white and brown adipocytes.

Preadipocytes

are unilocular, with one large lipid droplet occupying most of the cytoplasm. The white adipocyte is usually much larger than that shown here in relation to the other cell types.

White Adipocytes

differentiate from another population of preadipocytes located in paraxial embryonic mesoderm and remain multilocular (having many small lipid droplets) with numerous mitochondria (not shown here).

Brown Adipocytes

Brown Adipocytes differentiate from another population of preadipocytes located in ___________________and remain multilocular (having many small lipid droplets) with numerous mitochondria (not shown here).

paraxial embryonic mesoderm

Preadipocytes developing within the _________ of the embryo

lateral mesoderm

contains cells with multiple lipid droplets interspersed among abundant mitochondria, o develops from mesenchyme.

BROWN ADIPOSE TISS

contains brown adipocyte which release heat and function to warm the blood.

BROWN ADIPOSE TISSUE

surrounded by a thin external lamina containing type IV collagen

BROWN ADIPOSE TISSUE

constitutes 2%-5% of the newborn body weight, located mainly in the back, neck, and shoulders, but it is greatly reduced during childhood and adolescence.

BROWN ADIPOSE TISSUE

found only in scattered areas, especially around the kidneys, adrenal glands, aorta, and mediastinum. (adults)

greatly reduced during childhood and adolescence o color is due to both the very abundant mitochondria (containing cytochrome pigment) scattered among the lipid o amount is maximal relative to body weight at birth

BROWN ADIPOSE TISSUE

very abundant mitochondria (containing ________ pigment)

cytochrome

contain many small lipid inclusions and are therefore called multilocular

Brown Adipocytes

Brown Adipocytes contain many small lipid inclusions and are therefore called _______

multilocular

small lipid droplets, abundant mitochondria, and rich vasculature

Brown Adipocytes

often closely packed around large capillaries produce heat by nonshivering thermogenesis number increases during cold adaptation

Brown Adipocytes

often closely packed around large capillaries produce heat by nonshivering _______

thermogenesis

are slightly smaller and characteristically contain many small lipid droplets and central spherical nuclei. If the lipid has been dissolved from the cells, as shown here, the many mitochondria among the lipid spaces are retained and can be easily discerned.

Brown Adipocytes

emerge earlier than white fat during fetal development.

Brown adipocytes

ending that releases norepinephrine to stimulate mitochondrial production of heat, the principal function of brown adipose tissue.

sympathetic nerve

The physiology of brown fat is best understood from studies of the tissue in hibernating species.

BROWN ADIPOCYTES

As in white fat, this neurotransmitter activates the hormone-sensitive lipase of adipocytes, promoting hydrolysis of triglycerides to fatty acids and glycerol.

BROWN ADIPOCYTES

Liberated fatty acids of multilocular adipocytes are not released but are quickly metabolized, with a consequent increase in O2 consumption and heat production. This raises the temperature within the tissue and warms the locally circulating blood, which then distributes the heat throughout the body

BROWN ADIPOCYTES

1. White adipocytes are derived developmentally from what precursor cells?

c. Mesenchymal cells

2. What are the relatively large particles formed in the intestinal epithelial cells and rich in ingested lipids?

b. Chylomicrons

3.What substance, released from the adrenal gland and some autonomic neurons, increases lipolytic activity in white adipocytes?

c. Norepinephrine

4. What is the most important form of lipid storage in both white and brown adipocytes?

e. Triglycerides

5. Important target cells of leptin are found in which organ?

d. Hypothalamus

6. The hormone-sensitive lipase in the cells of adipose tissue acts primarily on what substrate?

d. Triglycerides

7. Applied to adipocytes, the term “multilocular” refers to which of the following?

a. The large number of small cytoplasmic lipid droplets

8. Fully differentiated white adipocytes are large cells, typically having diameters of approximately what size?

c. 100 μm

CHAPTER 6: ADIPOSE TISSUE Flashcards

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