Lecture 9 & 10 - Glands & Connective Tissue Flashcards
What type of gland is the parotid gland,? What type of duct does it have and why? Explain sequence of duct.
- Serous gland: store inactive proenzyme
- Striated duct to prevent water loss (reabsorb Na+ and CI- ions –> hypotonic saliva produced)
(Acinus –> intercalated duct –> striated duct –> excretory duct)
AISE
**Parotid gland occurs in pairs
Why is mucous acini paler than serous?
- Mucin X bind to H&E
- Need Alcian blue stain
Compare the type of gland in parotid, submandibular and sublingual gland
- Parotid: almost all serous gland
- Submandibular: mostly serous, some mucous
- Sublingual: mostly mucous
What is the function of parotid gland? What causes a blockage in parotid gland ducts and what treatment for it?
- Parotid gland secrete saliva
- Blockage caused by bacterial/viral infection (common) or tumour (rare) –> parotitis & intense pain
- Treatment w antibiotics and abscess drainage/surgery
What is the type of control for salivary gland?
Neural control ONLY
*Other digestive secretion is hormonal
Compare the different type of capillary vessels
location, structure, function
- Continuous: Thick basement membrane, no holes –> prevent leakage (Blood-brain barrier)
- Fenestrated: Basement membrane has small holes to allow small molecules to pass through –> small intestine
- Sinusoid: Incomplete basement membrane –> spleen/bone marrow/liver
How to recognise stuff in liver lobule
- Hepatocytes: 2/3 nuclei
- Portal vein: Largest lumen
- Hepatic artery: small lumen
- Bile duct: darkly stained, small lumen
N.B Bile duct next to tight junction (X seen on slide, jus saying)
What is the function of a pit cell?
- Kill tumour cells that enter sinusoids
What are Kupffer cells and where are they found? Function?
- Found in small gaps btw hepatocytes (look flat, jelly ish w nucleus)
- Specialised macrophages (80% of all macrophages)
- Function: Phagocytose dmg/aged RBC that are missed by spleen (recycle RBC –> globin chain re-use, haem broken down to iron, bilirubin to bile)
- Kupferr cell activation is responsible for early-ethanol induced liver injury
- In event of splenectomy, they takeover removal of RBC (120 days)
What are Stellate (Ito) cells function? What happens in liver cirrhosis?
- Store Vit A
- In L.C, lose ability to store vit A –> differentiate into myofibroblasts –> synthesise/deposit collagen in perisinusoidal space –> liver fibrosis
*Look like one big cell w lipid droplets in btw 2 hepatocytes
What are structural features of hepatocytes?
- Good regenerative ability
- ⬆️Mitochondria, free ribosome, RER, SER, Golgi & glycogen (darkly staining balls)
- Binucleated
What are the liver functions?
Largest exo/endo gland in body
- Storage for iron, vit A, glycogen (& copper)
- Produce enzymes (ALT/AST), albumin, lipid carrier proteins.
- Produce IGF, thrombopoietin, angiotensinogen
- Hemopoiesis in fetus
- Breakdown drugs, hormones, conjugate bilirubin
- Bile production
- Emulsify fats
Desc liver regeneration in 50% (low to mild) dmg, 70% (medium), >70% (severe) dmg
- Low to mild
- Due to viral infection & alcohol use
- 7-8 days - Medium
- Liver transplant/drug toxicity (paracetamol)
- 30-40 days - Severe
- Liver failure/cirrhosis/alcohol misuse
- Never
What is the structure of connective tissue?
- Cells: fibroblasts
- Fibres: collagen, elastin
- Ground sub: proteoglycan
N.B Ground sub + fibre = extracellular matrix
What is the function of connective tissue?
- Binding and supporting (holding skin)
- Protecting vital organs (bone/fat act as shock absorber)
- Separation of tissues (fascia/cartilage)
What are the two types of connective tissue? Examples
- Loose connective tissue
- Known as areolar (little space) tissue
- Lamina propia in mucosal membrane, submucosa - Dense connective tissue
- Fibrous/collagenous tissue
- 2 types: irregular (diff directions) & regular (parallel fibres)
Function of areolar tissue
- Holds tissues to tissues
- Allow cell migration
- Acts as packaging around organs
Function of fibroblasts. What are myofibroblasts?
- Synthesise fibres (of ground substance)
- Important in wound healing/scar formation
- Modified fibroblasts that contain actin and myosin. Responsible for wound contract
(Ito/stellar cells in liver lose ability to store Vit A and form these during liver cirrhosis, scar tissues)
What are the function of mast cells? Location?
- Contain:
i) Histamine (increase blood vessel wall permeability)
ii) Heparin (anticoagulant)
iii) Cytokines (attract eosinophils and neutrophils) - Found in areolar tissue near blood vessels
- Coates w IgE –> foreign antigen come in contact –> contents released
Where are Mast cells not found in the body and why?
- X found in CNS to prevent oedema
What is the function of white adipocytes in loose connective tissue?
- Shock absorber
* difficult to see in H&E stain bcs toluene hydrolysed all lipid. Nucleus usually in periphery
What is the func. of brown adipocytes in areolar tissue?
- Very few in adults (shivering)
- Provide insulation and energy reserve
(Structure: Multiple small lipid droplets. Nucleus, cytoplasm n organelles squeezed in centre)
What is the difference of white and brown adipocytes?
*generated from mesenchymal stem cells/immature fibroblasts
White:
- Single lipid droplet
- Normal no. of mitochondria
- Single peripheral nucleus
- In adults, lipid breakdown is slow and heat generation thru shivering
Brown:
- Multiple lipid droplets
- ⬆️mitochondria
- Single central nucleus
- Accelerated lipid breakdown, oxidative phos. for heat
Desc the types of collagen
- Type I - Most abundant. Aggregate to form fibres and fibre bundles (tendon, dermis, capsules of organs)
- Type II - X form fibres (hyaline & elastic cartilage)
- Type III - Form fibres around muslce/nerve cells/lymphatic tissue & lymph. organs/tendons. Called reticulin
- Type IV - Basement membrane
What is extracellular matrix?
Complex extracellular structural network that consists of ground sub (proteoglycan/hyaluronic acid) and fibres
What are the diff types of fibres in connective tissues and their functions?
- Collagen: Flexible w high tensile strength
(thicker lines than elastin) - Reticulin: Provide supporting framework
[absent in areolar] - Elastin: Allows tissue to recoil after stretch
(look like small thin lines)
Where is loose areolar tissue found and why?
- Beneath epithelia (etc. glands) and around small blood vessels [submucosa of colon]
- Contain immune cells (macrophages) that can kill pathogens if they breach epithelial layer –> result in areolar tissue to swell (elastin fibres) –> return to ori. size after
What is ground substance and what is it made out of?
- Viscous, clear sub. with slippery feel (high water content)
- Composed of proteoglycans (large macromolecules with core protein that covalently binds to glycosaminoglycans, GAG)
- GAG is long polypeptide chain–> attract H2O, resists compression
(Hyaluronic acid eg. of GAG, bound to proteo- form hydrophilic mol.)
What is an example of location of irregular dense connective tissue? Why?
- Superficial layer of dermis
- Resist forces to prevent tearing of skin –> elastic fibres allow degree of stretch
(Have v little ground sub)
What is an example of location of REgular dense connective tissue? Why?
- In tendons (connect muscle to bone)
- Provides tremendous physiological stretch
What is tendon made out of?
30% collagen, 2% elastin, 68% water!
70% collagen I , 30% collagen III (reticulin)
What is the diff. & similarities btw irregular and regular dense connective tissue?
Both: Contain fibroblasts
Irregular:
- Collagen I fibres in all directions
- Resists stress in all directions
- Deep layer of dermis, deep fascia (covering large muscles)
Regular:
- Collagen I fibres parallel, resists strength in one direction
- Tendon. Ligament
What is the structure and func. of ligaments?
- Connect bone to bone
- Regular dense connective tissue
- Wrapped around irregular dense c.t –> fascicles
What is fascia? Function?
Hint: 3 types of fascia = superficial, deep, visceral/parietal
- Made of regular dense connective tissue
- resists tension in one direction
Desc collagen fibril production. What is the substance required for collagen prod?
- Fibroblasts secrete procollagen –> collagen outside cell –> collagen fibrils
- Collagen fibrils –> tendon/ligament/bone OR fascia
- Vit C required for production of procollagen: hydroxylates proline and lysine
- W/o Vit C collagen production is impaired
What is scurvy? What does it cause? Symptoms?
- Deficiency of Vit C
- Leads to impaired collagen production
- Symptoms:
i) Bleeding gums & tooth loss
ii) Bruising of skin and hair loss
iiii) Bleeding
iv) Poor wound healing
v) Impaired bone dev. in young
What is Marfan’s syndrome? What is it’s inheritance? Symptoms?
- Autosomal dominant disorder
- Expression of fibrillin 1 gene is affected –> abnormal elastic tissue
- Symptoms:
i) Tall
ii) arachnodactyly
iii) frequent joint dislocation
iv) ⬆️risk of aortic rupture
What are some signs of Marfan’s?
- Early onset of cataracts
- Steinberg Sign: When clenching fist, thumb is visibly popping out the other side
- Walker-Murdoch Sign: Put hand around wrist, thumb extends out
What are elastin fibres? Where are they found?
- Primary component of elastic fibres
- Surrounded by fibrillin (microfibrils)
- Found in dermis, artery walls, alveoli
What is Ehlers-Danlos syndrome? Causes what?
- Collagen fibre abnormalities in dermis and tendons
- Cause joint dislocation and skin deformation
What is lipomas?
- Benign tumours of adipose tissue
losing weight X decrease size of tumour
What is osteogenesis imperfecta? Mode of inheritance? Results in?
- Brittle bone disease due to mutated collagen fibres results in abnormal structure OR collagen fibres X produced
- Autosomal dominant
- Results in:
i) Weakened bones (fractures common)
ii) Short stature
iii) Blue sclera
iv) Hearing loss
v) Poor teeth dev.
Which layer of arteries is elastin fibres found? What produces them? Are they replaced if damaged?
- Found in tunica media
- Smooth muscle cell produces elastin, collagen and matrix
(fibroblasts –> scar tissue) - Elastin is formed in fetal dev, X again in adult
What happens to elastin COPD?
- COPD is emphysema and chronic bronchitis
- Alveoli elastic fibres is replaced w scar tissue –> permanent widening of air spaces
Name 6 types of connective tissue and general func. One similarity of all
- Blood: transport nutrients and waste products
- Adipose: insulation, shock absorber, energy reserve
- Areolar: holds tissues to tissues, permit cell migration
- Bone: attachment of muscles, protect organs
- Cartilage: protection, shock absorber
- Dense: connect bone to bone (ligament is dense regular)
- All derived from mesenchymal stem cell or immature fibroblasts
Function of bile
- Emulsify fats to ease breakdown of lipids by lipase
- Aid absorption of lipids and fat sol vit
What is the role of bac. in colon?
- Prevent other harmful bac from inhabiting colon
- Production of vit: K and B12
- Metabolise harmful products frm digestion of small intestine
What prevents bac from invading colonic wall?
- Layer of mucus = bac. X come into contact, prevent inflammation of colonic wall
- Sentinel cells = secrete mucus
Briefly desc what occurs in zones of liver
Zone 1:
- Specialise n oxidative liver func = gluconeogenesis
- β- oxidation of fats
- Cholesterol synthesis
Zone 2:
- Glycolysis
- Lipogenesis
- Cytochrome P-450 based drug detoxification
Zone 3:
- Highest drug detoxification
- CYP2E1 = ⬆️sensitivity to NAPQI
Where is mucous connective tissue found (also known as Wharton’s jelly)? What do they contain?
Umbilical cord
- Fibroblasts, macrophages, lymphocytes, neutrophils (infected pregnancy), hyaluronic acid in ground substance
- Type I and III collagen
How can fibroblasts be identified in C.T?
Red staining nuclei
