Histo Lecture 8
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What gives structure to adipose tissue?
Adipose tissue is lowly or highly vascularized?
Locations of Adipose tissue
- -Subcutaneous areas
- -Body cavities
- -Surrounding organs and tissues (nerves, vessels)
Functions of Adipose Tissue
- -Reservoir for lipid storage
- -Temperature insulation
Describe uniocular fat
- -"yellow fat"
- -Most common type
- -Single lipid droplet fills the majority of cellular cytoplasm
- -Nucleus and cytoplasm are "squeezed" into the periphery of adipocytes
Describe Multiocular fat
- -"Brown fat"
- -Infants and animals that hibernate
- -Limited amount in adults
Cytoplasm in multiocular fat contains:
- -Numerous lipid droplets
- -Many mitochondria
- -Central nucleus
How does multiocular fat produce heat?
Thermogenin shunts energy away from ATP production in the transmembrane protein of mitochondria to produce heat instead
How are lipids transported?
- -Lipids are attached to proteins which allows them to become "soluble" in plasma and allows cells to control entry and exit of lipid molecules
- -Vary in size (VLDL, LDL, HDL, IDL, chylomicrons)
- -Small particles (3μm in diameter) formed in the intestine and transported in plasma
- -Triglycerides packaged with cholesterol, phospholipids and proteins
Describe how lipids are acquired and stored
- -Most fatty acids have origins in dietary fats
- -During digestion, triglycerides are split into monoglycerides and fatty acids in the GI tract (transported as chylomicrons)
- -Liver synthesizes components into triglycerides which are then transported in form of VLDL
- -Liver can also convert glucose to fatty acids and glycerol
What is the function of Lipoprotein lipase?
- -Enzyme within endothelial cells of capillaries
- -Breaks down lipoproteins and releases FFA (free fatty acids) and glycerol
Triglycerides are stored in ______ within the cytoplasm
This hormone stimulates the uptake of glucose and adipocyte synthesis:
Lipids are mobilized from adipocytes in response to there two stimuli:
- -Hormonal stimuli (growth hormone, thyroid hormone, cortisol)
- -Neurogenis stimuli (norepinephrine)
Functions of Hormone Sensitive Lipase (HSL)
- -Becomes active when triglyceride release from adipocytes is stimulated
- -HSL hydrolyzes trigs into FFAs and glycerol
- -FFAs (bound to albumin) and glycerol diffuse into capillaries for distribution
Hormones that activate HSL
- Thyroid Hormone
- Growth Hormone
In what order are fats mobilized?
- -Fats in subcutaneous, mesenteric, and retroperitoneal areas are mobilized first
- -Adipose tissue in hands, feet, and retro-orbital fat pads resist long periods of starvation
Functino of Leptin
- -Protein produced by adipocytes
- -Regulates metabolism, energy intake and production
- -Acts on hypothalamus to decrease food intake and increase energy utilization
5 Types of anthropomety
- -Bod Pod
- -Underwater weighing
- -Electrical impedance
- -Skin calipers
Types of Obesity
- -Exogenous - caloric intake > caloric expenditure
- -Endogenous - metabolic cause (<1% of all cases)
Incidence of Obesity
- -64% of Americans are overweight
- -30% of Americans are obese
- -15% of American children are obese (ages 6-17)
- -Most at risk: Minorities, low income, lower education
Name some consequences of Obesity
- -Coronary artery disease
- -Type II diabetes
- -Gall bladder disease
- -Osteoarthritis (OA)
- -Sleep apnea
How do chronically trained muscles increase use of lipids?
- -Increase capillary/muscle fiber ratio
- -Increase # of mitochondria
- -Increase in oxidative enzymes which allow for icnreased aerobic capacity
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