Cytology week 9 (Got 3 content) Flashcards
Adipose Tissue
What is Adipose tissue?
Connective tissue that is dominated by fat stroing cells called adipocytes
Where and how can adipoctyes be found
-In small groups within connectove tissues or in large aggregates in organs
What are the 5 main functions of Adipose tissue
- Energy Storage
-Regulation of Metabolism
-Endocrine Role
-Thermal insulation
-Mechanical support
What are the types of Adipose tissue
- White Adipose tissue
- Brown Adipose Tissue
What is the function of white Adipose tissue
-Specialised for fat storage
What does white adipose tissue contain
- Large cytoplasmic droplets of whitish-yellow fat
What does brown adipose tissue contain
- Multiple lipid droplets
- Abundant Mitochondria
What is the function of the brown adipose tissue
- Releases heat to warm the blood
What is white adipose tissue composed of?
- Composed of large adipocytes with a single large triglyceride droplet
Why do adipocytes appear empty in slides
- Due to lipid removal
Explain the tissue structure of white adipose tisue
- The white adipose tissue is divided into lobules by connective tissue containing vascular bed and nerve networks
-Reticular fibres from a suppoertive network around adipocytes
-
White adipocytes can store triglycerides derived from what 3 sources
- Dietary fats
-Lipids synthesized in the liver
-Free fatty acids and glycerol
Explain how dietary fats are sources of triglycerides for storage( How are dietery fats transported
-Transported into the blood as chylomicrons, which are lipid particles formed in the small intestine
- Chhylomicorns
What does chylomicron contain
- Triglycerides
- Phospholipids
-Cholestrol
-Apolipoproteins
How are liver sythesized lipids transported in the blood
- As very low density lipoproteins (VLDLs)
- Smaller than chylomicrons, they are synthesized in the liver cells and categorised based on density
Where are free fatty acids and glycerol produced
- They are produced within adipocytes
Explain the triglycericde storage process
Hydrolysis of chylomicrons and VLDLs
- Occurs at capillary surfaces via lipoprotein lipase (synthesized by adipocytes).
-Free fatty acids enter adipocytes through active transport and diffusion.
-Fatty acids combine with glycerol phosphate (from glucose metabolism) to form triglycerides, stored in lipid droplets.
What is the role of insulin in the triglycerid storage process
- Stimulates glucose uptake and conversion into triglycerides
- Increase lipoprotein lipase producttion and inhibits lipid mobilization
Explain the stimulation process of lipid mobilization process
Stimulation:
Triggered by hormones (e.g., norepinephrine, growth hormone).
Hormone-sensitive lipase breaks down triglycerides into fatty acids and glycerol.
Explain the transport process in lipid mobilization
Transport:
Free fatty acids bind to albumin in blood for transport.
Glycerol is transported freely in blood and taken up by the liver.
Explain the regulation process in lipid mobilization
Regulation:
Insulin inhibits lipase activity, reducing fatty acid release and promoting lipid synthesis.
Other hormones (e.g., leptin) regulate appetite and adipose tissue formation.
Name the 3 processes in order in lipid mobilization
-stimulation
transport
regulation
Describe visceral fats
- Loacted in the abdomen
-Associated w increasing risk of diabetes and cardiovascular disease - Prodcuts are released directly to the portal circulation and liver
Describe subcutaneous fats
- Beneath the skin and is less associated w medical risks
Explain the development of white adipose tissue
-Adipocytes originate from mesenchymal stem cells.
-Development involves preadipocytes, which resemble larger fibroblasts with lipid droplets.
Lipid droplets in white adipocytes fuse into a single large droplet
How are beige adipocytes formed
-Beige adipocytes form alongside white adipocytes in white adipose tissue.
Explain how adipocytes are formed in adulthood
-New adipocytes arise near small blood vessels from undifferentiated mesenchymal cells.
When does obesity occur
When energy intake exceeds expenditure
In adulthood obesity what is there a increase in
- Adipocyte size
In childhood obesity what is there an increase in
- Adipocyte size and volume
Where is brow adipose tissue primarly located
- Back
-Neck
-Shoulders
Why does brown adipose tissue have a brown colour
- Due to abundant mitochondria and a rich capillary networl
Explain the quantities of brown adipose tissue during childhood+ adolesence compared to adulthood
- Amount of BAT is reduced during childhood and adolesence
- But persists/still present in adult areas like kidneys adrenal gland and aorta
What is the structure of Brown Adipose tissue
- Has polygonal cells, which are smaller than white adipocytes with a centrally located nuclei
-Organised into libules by connective tissue partitions
-
What are the functions of Brown Adipocytes
MAIN FUNCTION:- Heat production through non shivering thermogenesis
- Fatty acids are metaoblised within the cell, leading to increased oxygen consumption and heat production
- Nerve impulses relaease norepinephrine which activates hormone-sensitive lipase promtoing triglyceride breakdown
What is the general characteristics of Cartilage
- Cartilage is a tough and durable supporting connective tissue
-It is charcterised by an extracellular matrix with high concentration of glycosaminoglycans (GAGs) ,proteoglycans , collagen and elastic fibers - The ECM provides a firm consistency
What are the functions of cartilage
- Supports softer tissues in the respiratory tract, ears and nose
-Provides cushioning and smooth lubricated surfaces in joints to allow movement
What is cartilage composed of
-Composed of chondrocytes which are located in the matrix cavities called lacunae
What is the function of chondrocytes
- Synthesize and maintain all ECM components
Name the types of cartilage
- Hyaline Cartilage
-Elastic Cartilage
-Fibrocatrilage
Explain hyaline cartilage
- Where it is found
- And apperance
-Found in joints, respiratory structures, and growth plates; has a glassy ECM appearance.
Explain Elastic cartilage
-What it contains
-Where it is found
- Contains elastic fibers, providing flexibility
-Found in the ear and epiglottis
Explain Fibrocartilage
-what it contains
-where is it found
- Contains dense collagen fibers for strength
- Found in intervertebral discs and pubic symphis
What is the name of the 2 processes in which cartilage grows through
- Interstitial growth
-Appositional growth
What is the perichondrium and function
- It is a dense connective tissue that surrpunds cartilage
-Provides blood supply and a small neural component - Absent in articular cartilage
What is the most common type of Cartilage
Hyaline Cartilage
What is the role of hyaline in embryos
- Forms the temporary skeleton, which is later replaced by bone during development.
What does the Matrix of the hyaline cartilage contain and explain them
- Collagen: mostly type 2 collagen
-Proteoglycan: Embedded in a firm hydrated gel that gives the matrix its basophillic nature
-Structural Glycoproteins: Includes chondroncetin
Name and describe a type of proteoglcan in hyaline cartilage
- Aggrecan:
- It is the most abundant proteoglycan with a core protein
What is Chondroncetin
- It is a mulit adhesive glycoprotein
- It Facilitates the adhesion of chondrocytes to the extracellular Matrix
Name the two types of chondrocytes
-Peripheral chondrocytes
-Deeper chondrocytes
What is the function of chondrocytes
- They secrete collagen and ECM components
What is the perichondrium in the Hyaline Cartilage
- Dense connective tissue layer that covers the hyaline cartilage
What is the function of the perichondrium
- It is essential for cartilage growth and maintenance
Describe the structure of the perichondrium(outer layer and inner layer/what it contains)
-Outer layer: Composed mainly of type 1 collagen and fibroblasts
-Inner Layer: Contains mesenchymal stem cells
What is the structure of Elastic Cartilage
-Contains an abundant network of elastic fibers and type 2 collagen fibrils
What is the apperance of elastic cartilage and why
- Yellow colour due to the presence of elastic fibers
Where do Osteoblasts originate from
- Mesenchymal stem cells
What is the function of the Osteoblasts
Produce organic components of the bone matrix
-Type 1 collagen
Proteoglycans
-matricellular glycoproteins
Where are osteoblasts located
On the bone matrix surfaces
What happens to osteoblasts after activity
- Differentiate into osteocytes
- Undergo apoptosis
-flatten to become bone lining
How do osteocytes form
When osteoblasts become surrounded by the matrix
Where is Osteocytes found
- Enclosed in the lacunae
What is the function of osteocytes
- Acts as mechanosensors, detecting mechanical load and microdamage to the bone
- ## Produce proteins with paracrine and endocrine effects that regulate bone remodelling
Compare the Osteocyte structure to the Osteoblasts
Osteocytes have:
-Less RER, smaller Golgi complexes
- More condensed nuclear chromatin
What is the structure of Osteoclasts
-Large,multinucleated motile cells
How are osteoclasts formed
By the fusion of marrow-derived monocytes
What is the role of Osteoclasts in Bone remodelling
- Reabsorbing the bone matrix
What do osteoclats require for activation/development
- M-CSF (macrophage-colony-stimulating factor)
RANKL
