Lecture 5 - Tissues, Organs And Systems Flashcards
What is a tissue?
A group of structurally similar cells that function together as a unit
What 4 things holds cells together?
Cell to cell adhesion molecules
Extracellular matrix proteins (fibres)
Internal-external scaffolding
Close proximity (pressure effects)
What do epithelial cells normally rest on top of?
Basement membrane between them and A supporting bed of connective tissue
What usually separate epithelial cells and the supporting bed of connective tissue?
A basement membrane
What is the definition of an organ?
Multiple tissues coming together
How are epithelial cells held together?
Through epithelial cell adherence systems
Where are adherence systems found on/in an epithelial cell?
The lateral surface
The basal surface
What is the role of the adherence systems found on the lateral surface of an epithelial cell?
Joins epithelial cells to epithelial cells
What is the role of the adherence systems found on the basal surface of an epithelial cell?
They join the epithelial cell to the basement membrane
What 4 epithelial adherence systems are located on the lateral surface of the epithelial cells?
Tight junctions
Adherens junctions (cadherins)
Desmosomes
Gap junctions
What is the function of the tight junction adherence system? (Lateral surface)
Seals neighbouring cells together in an epithelial sheet to prevent the leakage of molecules between the cells
What is the function of the Adherens junction adherence system? (Lateral surface)
(Cadherins)
Joins an actin bundle in one cell to a similar bundle in a neighbouring cell
What is the function of the Desmosome adherence system? (Lateral surface)
Joins the INTERMEDIATE filaments in one cell to those in a neighbour
What is the function of the gap junction adherence system? (Lateral surface)
Allows the passage of small water soluble ions and molecules
Allows for very quick communication between cells
Which of the lateral surface adherence systems is the strongest
Desmosomes
What are the 2 important adherence systems located on the basal surface of epithelial cells?
Hemidesmosomes
Focal adhesions (Integrins)
What is the function of the hemidesmosome adherence system? (Basal surface)
Anchors intermediate filaments in a cell to the basal lamina
What is the function of the focal adhesion adherence system? (Basal surface)
(Integrins)
Anchors actin filaments in a cell to the basal lamina
Which of the 2 adherence systems joins actin?
Adherens junction (Lateral surface) cadherins
Focal adhesion (Basal surface) Integrins
So cadherins and Integrins join actin, Cadherins actin cell to cell and Integrins actin from cell to basement membrane
Which of the 2 adherence systems join intermediate filaments?
Desmosomes (Lateral surface)
Hemidesmosomes (Basal surface)
What adherence system is very important for communication between cells that can touch each other?
Gap junctions
How do tissues adhere to other types of tissues?
Through connective tissue fibres
What is the 2 main functions of adherence proteins?
Maintain survival and structure of the cells and tissues
Prevent pathogenic entry into the internal environment
What is the definition of a Mucosal Membrane?
The moist, inner lining of some organs and body cavities
What do the glands in the mucous membrane produce
Mucus
Where do musical membranes line?
GI Tract
Urinary Tract
Respiratory Tract
Urogenital tract
What is mucous made of?
Mucins (Proteins made by goblet cells)
Water
Electrolytes
Antiseptic enzymes
Immunoglobulins
What are the 3 functions of mucosal membranes?
Stops pathogens and it entering the body
Prevent dehydration of body tissues
Lubrication
What happens when Collagen 4 is mutated?
Thin Basement membrane syndrome
Causes lung disease and kidney disease
What are the layers of the GI tract from the lumen deeper into the tissue?
Epithelial mucosal cells line lumen
Lamina Propria
Muscularis mucosae (thin smooth muscle layer)
Submucosa = Connective tissue with arteries and veins
Muscularis externa = smooth muscle layer with muscle fibres going in 2 different directions
Serosa = Connective tissue layer
What is the Muscularis mucosae?
Thin smooth muscle layer
What is submucosa?
Connective tissue layer with arteries and veins
What 2 directions do the smooth muscle fibres go in in the Muscularis externa?
Inner circular muscle
Outer longitudinal muscle
What does the Serosa connective tissue contain?
Collagen and elastin fibres
Small arteries and veins (maybe nerves)
How is the structure of the Epithelial mucosa of the oesophagus related to its function?
Stratified squamous non-keratinised
Withstands abrasion
What does the submucosa do in the oesophagus?
Connective tissue joining epithelialmucosa to Muscularis externa
Contains mucus secreting glands
What is the function of the Muscularis externa in the oesophagus?
Smooth muscle layers which allow food to be moved by peristalsis and for the oesophagus to return to its original shape
What are the 3 layers of smooth muscle in the Muscularis externa of the stomach?
How does this differ to the smooth muscle of the Muscularis externa of the rest of the GI tract (oesophagus, small intestine and large intestine)?
Oblique
Circular
Longitudinal
Reset = inner circular and outer longitudinal
What are the 3 functions of mucosa in the GI tract?
Absorb substances from the lumen
Prevent ingress of pathogens
Move contents and expel waste
How does the mucosa of the GI tract allow it to absorb substances from the lumen?
Folding of mucosa (SA)
Microvilli (SA)
How does the mucosa of the GI tract allow it to prevent ingress of pathogens from the lumen?
Carries out peristalsis
Lamina propria contains lymphatic tissue
How does the mucosa of the GI tract allow it to move contents and expel waste from the lumen?
Muscularis externa performs peristalsis
What is the structural unit of the kidney?
Nephron
What is the function of the nephron?
Remove/filter waste from the body
What type of epithelial cells are present in the glomerulus/corpuscle of the nephron?
Squamous epithelial cells
What type of epithelial cells line the nephron collecting ducts?
Cuboidal epithelial cells
In the urinary tract, where does the muscle layer first start to appear?
Ureter and bladder
Describe the structure of the mucosal membrane in the ureter:
Transitional epithelial cells line lumen
Lamina propria connects epithelium to Muscularis mucosae (smooth muscle)
Surrounded by Muscularis externa
Where are Transitional epithelial cells usually found?
In the Urinary tract
What is the other name give to transitional epithelial cells?
Urothelium or Umbrella cells
What is the function of the Urothelium, umbrella cells or Transitionl epithelial cells in the urinary tract?
Ensures urine stays in Urinary tract
Produce mucus
Protects bladder from damage from acidic urine
Tigh junctions and well packed together helps protect inner cell layers from damage
What is the function of the Urinary tract?
Absorption of essential nutrients in the kidney
Prevent pathogen entry
Remove waste products
What is special about the mucus glands in the urethra?
Produce lots of sticky mucus to prevent ingress of pathogens
What is special about the Urothelium cells in the urethra?
Change to squamous then keratinised squamous epithelium at outlet
What is the function of the respiratory tract?
Gaseous transport and exchange
What are the 2 parts which the respiratory tract is divided into?
Conducting portion
Respiratory portion
What is part of the conducting portion of the respiratory tract?
Nasal cavity to bronchioles
What is part of the respiratory portion of the the respiratory tract?
Respiratory bronchioles to alveoli
What is special about the structure of the trachea despite it containing mucous membranes?
Has no outer layer of smooth muscle (muscularis externa)
Contains C shaped hyaline cartilage to keep trachea open
Describe the structure of the trachea and primary bronchi:
Mucosa = Pseudostratified ciliates columnar epithelium , lamina propria
Submucosa = Connective tissue layer = collagen, elastin and fibroblasts, seromucous glands make watery mucus
C-shaped hyaline cartilage
What is contained in the secretions from the epithelium and submucosal glands of the trachea and bronchi?
Mucins and water
Serum proteins (Lubrication)
Lysozyme (destroys bacteria)
Anti-proteases (inactivates bacterial enzymes)
What is the function of cilia in the trachea?
Beat synchronously to waft mucus containing pathogens or dirt to be swallowed
WHat do goblet cells do?
Produce Mucins which is the sticky component of mucus
How is the histology of secondary and tertiary bronchi different to primary bronchi?
C shaped hyaline cartilage no longer present as full circle of rings
BOTH HAVE NO OUTER LAYER OF SMOOTH MUSCLE
What is the function of collagen and elastin in the structure of the alveolus?
Collagen provides strength holding everything in place
Elastin allows alveolus to expand and elastically recoil back into its shape when empty
What is the type of epithelial cell that lines the alveolus?
Simple squamous epithelial cells
What is the basement membrane made up of that is found between the epithelial layer and the underlying connective tissue?
Basal lamina
Reticular layer
