Adipose Tissue HISTOLOGY
OUTLINE ● Fibroblasts, m phages, and other cells typically comprise about
half the total cell number in white adipose tissue.
l. Adipose Tissue ● Reticular fibers form a fine interwoven network that supports
II. White Adipose Tissue
individual fat cells and binds them together
Storage & Mobilization of Lipids
● The distribution of white adipose tissue changes significantly
Histogenesis of White Adipose Tissue
III. Brown Adipose Tissue through childhood and adult life and is partly regulated by sex
Function of Brown Adipocytes hormones
Histogenesis of Brown Adipose Tissue
ADIPOSE TISSUE
● CT in which fat-storing cells (adipocytes) predominate
● Typically found isolated or in small groups within loose/dense
irregular CT but occur in large aggregates in adipose tissue or
“fat” in many organs and body regions
● Represents 15-20% of the body weight in men
● Serve as storage depots for neutral fats, chiefly triglycerides
(long-chain fatty acyl esters of glycerol)
● Key regulators of the body’s overall energy metabolism
● Provides thermal i lation for the body
● Help shape the body surface, and cushion regions subject to
repeated mechanical stress such as the palms, heels, and toe
pads.
● Adipocytes
○ active cells metabolically, responding to both nervous and
hormonal stimuli
○ They release hormones and various other important Storage & Mobilization of Lipids
substances and adipose tissue is now recognized as an
endocrine organ at the center of nutritional homeostasis. ● White adipocytes can store triglycerides derived from three
● Two major types of adipose tissue sources:
○ 1. White adipose tissue ○ Dietary fats brought to the cells via the circulation as
■ more common type chylomicrons,
■ specialized for fat storage ○ Lipids synthesized in the liver and transported in blood with
■ consists of cells each containing one large cytoplasmic very-low-density lipoproteins (VLDLs),
droplet of whitish-yellow fat ○ Free fatty acids and glycerol synthesized by the adipocytes.
○ 2. Brown adipose tissue ● Chylomicrons
■ contains cells with multiple lipid droplets interspersed ○ from ingested lipids in epithelial cells lining the small intestine
among abundant mitochondria, which helps give this tissue and transported in the blood and lymph
a darker appearance. ○ consist of a core containing mainly triglycerides, surrounded
■ Release heat and function to warm the blood by a stabilizing monolayer of phospholipids, cholesterol, and
○ Both types of adipose tissue have a rich blood supply and the several apolipoproteins.
adipocytes are individually surrounded by a thin external ● VLDLs
lamina containing type IV collagen. ○ smaller complexes of similar lipid and protein composition to
chylomicrons, but are synthesized from lipids in liver cells.
● In adipose tissue both chylomicrons and VLDLs are hydrolyzed
MEDICAL APPLICATION at the luminal surfaces of blood capillaries by lipoprotein lipase
● Lipomas - benign tumors that unilocular adipocytes generate ● Lipoprotein lipase
○ relatively common ○ an enzyme synthesized by the adipocytes and transferred to
● Liposarcomas - malignant adipose tumors the capillary cell membrane
○ occur infrequently ● Fatty acids
● Hibernomas - Fetal lipomas of brown fat ○ enter the adipocytes by both active transport and diffusion
○ Within the adipocytes, the fatty acids combine with glycerol
phosphate, supplied by glucose metabolism, to again form
WHITE ADIPOSE TISSUE triglycerides, which are then deposited in the growing lipid
droplet.
● Long-term energy storage
● Insulin - stimulates glucose uptake by adipocytes and
● Adipocytes of white adipose tissue are spherical when isolated
accelerates its conversion into triglycerides, and the production
but are polyhedral when closely packed in situ
of lipoprotein lipase
● Very large, contains a single huge droplet of lipid filling almost
● When adipocytes are stimulated by nerves or various hormones,
the entire cell
stored lipids are mobilized and cells release fatty acids and
● White adipocytes - aka unilocular, with the single large droplets
glycerol.
of triglycerides
○ Norepinephrine - released in the adrenal gland and by
● signet-ring appearance - with the lipid droplet displacing and
postganglionic sympathetic nerves in adipose tissue activates
flattening the nucleus against the cell membrane
a hormone-sensitive lipase that breaks down triglycerides at
● The thin, submembranous layer of cytoplasm surrounding the
the surface of the stored lipid droplets.
lipid droplet contains cisternae of smooth ER (SER) and
○ stimulated by growth hormone (GH) from the pituitary gland
pinocytotic vesicles.
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OUTLINE ● Fibroblasts, m phages, and other cells typically comprise about
half the total cell number in white adipose tissue.
l. Adipose Tissue ● Reticular fibers form a fine interwoven network that supports
II. White Adipose Tissue
individual fat cells and binds them together
Storage & Mobilization of Lipids
● The distribution of white adipose tissue changes significantly
Histogenesis of White Adipose Tissue
III. Brown Adipose Tissue through childhood and adult life and is partly regulated by sex
Function of Brown Adipocytes hormones
Histogenesis of Brown Adipose Tissue
ADIPOSE TISSUE
● CT in which fat-storing cells (adipocytes) predominate
● Typically found isolated or in small groups within loose/dense
irregular CT but occur in large aggregates in adipose tissue or
“fat” in many organs and body regions
● Represents 15-20% of the body weight in men
● Serve as storage depots for neutral fats, chiefly triglycerides
(long-chain fatty acyl esters of glycerol)
● Key regulators of the body’s overall energy metabolism
● Provides thermal i lation for the body
● Help shape the body surface, and cushion regions subject to
repeated mechanical stress such as the palms, heels, and toe
pads.
● Adipocytes
○ active cells metabolically, responding to both nervous and
hormonal stimuli
○ They release hormones and various other important Storage & Mobilization of Lipids
substances and adipose tissue is now recognized as an
endocrine organ at the center of nutritional homeostasis. ● White adipocytes can store triglycerides derived from three
● Two major types of adipose tissue sources:
○ 1. White adipose tissue ○ Dietary fats brought to the cells via the circulation as
■ more common type chylomicrons,
■ specialized for fat storage ○ Lipids synthesized in the liver and transported in blood with
■ consists of cells each containing one large cytoplasmic very-low-density lipoproteins (VLDLs),
droplet of whitish-yellow fat ○ Free fatty acids and glycerol synthesized by the adipocytes.
○ 2. Brown adipose tissue ● Chylomicrons
■ contains cells with multiple lipid droplets interspersed ○ from ingested lipids in epithelial cells lining the small intestine
among abundant mitochondria, which helps give this tissue and transported in the blood and lymph
a darker appearance. ○ consist of a core containing mainly triglycerides, surrounded
■ Release heat and function to warm the blood by a stabilizing monolayer of phospholipids, cholesterol, and
○ Both types of adipose tissue have a rich blood supply and the several apolipoproteins.
adipocytes are individually surrounded by a thin external ● VLDLs
lamina containing type IV collagen. ○ smaller complexes of similar lipid and protein composition to
chylomicrons, but are synthesized from lipids in liver cells.
● In adipose tissue both chylomicrons and VLDLs are hydrolyzed
MEDICAL APPLICATION at the luminal surfaces of blood capillaries by lipoprotein lipase
● Lipomas - benign tumors that unilocular adipocytes generate ● Lipoprotein lipase
○ relatively common ○ an enzyme synthesized by the adipocytes and transferred to
● Liposarcomas - malignant adipose tumors the capillary cell membrane
○ occur infrequently ● Fatty acids
● Hibernomas - Fetal lipomas of brown fat ○ enter the adipocytes by both active transport and diffusion
○ Within the adipocytes, the fatty acids combine with glycerol
phosphate, supplied by glucose metabolism, to again form
WHITE ADIPOSE TISSUE triglycerides, which are then deposited in the growing lipid
droplet.
● Long-term energy storage
● Insulin - stimulates glucose uptake by adipocytes and
● Adipocytes of white adipose tissue are spherical when isolated
accelerates its conversion into triglycerides, and the production
but are polyhedral when closely packed in situ
of lipoprotein lipase
● Very large, contains a single huge droplet of lipid filling almost
● When adipocytes are stimulated by nerves or various hormones,
the entire cell
stored lipids are mobilized and cells release fatty acids and
● White adipocytes - aka unilocular, with the single large droplets
glycerol.
of triglycerides
○ Norepinephrine - released in the adrenal gland and by
● signet-ring appearance - with the lipid droplet displacing and
postganglionic sympathetic nerves in adipose tissue activates
flattening the nucleus against the cell membrane
a hormone-sensitive lipase that breaks down triglycerides at
● The thin, submembranous layer of cytoplasm surrounding the
the surface of the stored lipid droplets.
lipid droplet contains cisternae of smooth ER (SER) and
○ stimulated by growth hormone (GH) from the pituitary gland
pinocytotic vesicles.
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