BL L8 Flashcards
Name two types of membranes
- Mucous membrane
2. Serous membrane
Describe the mucous membrane, include what it lines and examples (more info in BL L7)
Lines certain tracts open to the exterior
E.g. GI, UT, Respiratory
The three mucosa layers
Describe the serous membrane, include what it lines, which they exude, examples, structure
Two part membrane which lines certain closed body cavities (spaces not open to the exterior) and envelop the viscera (internal organs of the body)
They line:
- peritoneum (envelopes many abdominal organs and GI tract)
- pleural sac (envelops the lungs)
- pericardial sac (envelops the heart)
Exude: Exude (don’t say excrete) a lubricating fluid (like a serum) that promotes relatively friction-free movement of the structures they surround.
Consists of:
- Simple squamous epithelium that exudes watery lubricating fluid
- Thin layer of connective tissue
- Doesn’t have a smooth muscle layer (whereas, the mucosal membrane has the muscularis mucosae layer)
Describe the structure of the serous membrane in more detail (3 parts of it)
(like a balloon with a hand in, hand is the visceral)
- Visceral serosa - inner membrane
- Lubricating serous cavity - between the inner and outer membrane
- Parietal serosa - outer membrane
ORGANS DO NOT LIE WITHIN THE SEROUS CAVITY ITSELF, BUT ARE SURROUNDED BY IT
What is the serous membrane the lungs are ‘sat’ in?
Pleurae sac
What is the serous membrane the heart are ‘sat’ in?
Pericardial sac
What is the serous membrane the abdominal organs and GI are ‘sat’ in?
Peritoneum sac
Define epithelial cells
Sheets of contiguous cells, of varied embryonic origin, that cover the surface of the body and line the internal surfaces, including the body’s vessels.
Embryologic origin
Ectoderm - e.g. the epidermis
Mesoderm - e.g. the inner linings of body cavities
Endoderm - e.g. the inner and outer lining of the GI
(can see the link)
What type of epithelial cells are serous membrane?
Simple squamous
Name the four types of simple epithelial cells
Squamous
Cuboidal
Columnar
Pseudostratified
Name the four types of stratified/compound epithelial cells
(more than one cell layer thick - e.g. 2, 7, 16 etc) Squamous Cuboidal Columnar Transitional
Which layer of stratified epithelial cells determines it’s type?
Apical layer (top layer)
Characteristics of simple epithelial cells
- One cell thick
- All have the nucleus at about the same height
Characteristics of stratified epithelial cells
- Two or more cells thick
- The type it is depends on the top cells in the top layer
What layers make up the basement membrane?
Basal lamina (thick gel like fluid) and reticular layer (net of collagen fibres)
What is the function of the basement membrane?
Provides support to the overlying epithelium cells and it limits contact between epithelial cells and other types of cells
Simple squamous epithelial cells: definition, functions and examples (need to learn examples)
Definition:
Single layer of flat cells in contact with the basal lamina
Functions:
- Fast material exchange and barrier to fluids
Example:
Bowman’s capsule (not ducts), serosa of lungs, heart and viscera
Simple cuboidal epithelial cells: definition, functions and examples (need to learn examples)
Definition:
A single layer of polygonal cells (they have many sides) whose width is equal to height
Functions:
- Absorption and secretion (kidneys and tubules)
- Absorption and conduit (ducts)
Examples:
Ducts
Simple columnar epithelial cells: definition, functions and examples (need to learn examples)
Definition:
A single layer of cells, whose heights are significantly greater than their widths
Functions: Absorption (small intestine and colon), secretion (stomach lining), lubrication (small intestine and colon)
Example:
Crypts of Lieberkun in large intestine, villi lining the small intestine
Pseudostratified epithelial cells: definition, functions and examples (need to learn examples)
Tissues in which all cells make contact with the basement membrane, but not all of the cells reach the epithelial cell surface. This results in nuclei lying at different levels, giving the impression of multiple layers.
Function:
Secretion and conduit, mucus secretion (respiratory tract), particle trapping and removal (respiratory tract)
Examples:
Nose (ciliated pseudostratified epithelial cells here)
What are basal bodies?
Basal body is a protein structure at the base of cilia
What does cilia ‘beat’ mean?
Cilia move
For an average sized man, how much fluid is in the plural cavities?
5ml in each, so 10ml overall
Stratified squamous epithelial: definition, example
Contain multiple layers of cells, the outermost (top apical layer) of which are thin squamous epithelial cells.
Cells are attached to each other rather than every cell being attached to the membrane (meaning there are certain properties holding them together - L7)
Functions include:
protection against abrasion
Example:
Non-keratinised example is the epithelium of the vagina and oesephagus
Stratified squamous keratinised epithelium: definition, example
Contains multiple layers of cells, the outermost of which are squamous that have lost their nuclei.
Functions (include): Protection against abrasion and physical trauma, prevention of water loss, prevention of microbial ingress, shielding against UV light damage
Example: Epidermis (skin)
What does keratinised mean? What is the role of the cornified layer?
The outermost dead cells (no nucleus) of this epithelium are collectively called the cornified layer
The cornified layers role -
- greatly reduces water loss and ingress
- prevents ingress of toxins like carbon dioxide
- protections against abrasion
- reduces microbial colonisation (at cornified layer is dry, no water here, microbes need water to colonise)
Epidermis: type of epithelial cell it is, 2 main layers in the epidermis, also talk about the major type of cell it contains
Stratified squamous keratinised epithelium
Very thick keratinised layer
Epidermis - dead keratinised and living epidermal cells
Dermis - connective tissue
Major cell is contains:
Keratinocytes (cells that mainly make up the epithelial cells).
- Keratinoctyes divide by mitosis, occur mainly in the basal layer
- Daughter keratinocytes then move towards the surface differentiating and losing their ability to divide
- Called keratinocytes because they synthesis keratins (fibrous proteins). Keratins contribute to the strength of the layers in the epidermis.
What is the normal transit time of a keratinocyte from basal layer to stratum cornuem?
28-40 days
Is the transit time of a keratinocyte faster or slower for younger people?
Faster for younger people
Describe what is happening is psariasis
The transit time is greatly reduces (2-4 days), therefore the stratum corneum is produced in abundance of silvery scales. Top layer is very fragile.
What are melantocytes?
These cells are in skin
occur at intervals (1 in 8 cells of the basal layer of the epidermis)
produce melanin which is the main pigment that gives skin its colour
darker skin = produce more melanin, do not increase the number of melanocyte cells
Mature melanosomes containing melanin are transferred to neighbouring keratinoctyes by pigment donation, keratinocytes are ‘phagocytising’ when they take a bit of the melanoctye into their cells.
What are Langerhan cells?
These cells are in the skin
highly specialised capacity to present antigens to T lymphocytes that mediate the immune reactions
Transitional epithelium: definition, example
Definition: Surface cells vary in shape from columnar/cuboidal to flattened
Usually columnar/cuboidal is the relaxed state and flattened is the stretched state.
Functions include: Protection of the underlying tissue from toxic chemicals
Example:
Location is the UT (renal calyces, ureters, bladder, proximal urethra)
Cell surface specialisations: Keratin - 2 functions
Prevents water loss and protects against abrasion
Cell surface specialisations: Cilia
Controls micro-movement of the luminal contents
Cell surface specialisations: Club cells
Protect bronchioles and acts as stem cells for respiratory epithelium (RT)
Cell surface specialisations: Stereocilia
In the auditory system, converts pressure waves into electrical signals
Goblet cells - more detail
Goblet cells do not have cilia on the apical surface, instead have microvilli
They release mucins through exocytosis
Ciliated cells release chloride ions
Water moves over as it is attracted by the osmolyte chloride ion
Water makes the mucus less ‘sticky’
What happens when there is a deficiency of chloride ions released?
Results in very sticky and immovable mucous
Characteristics of cystic fibrosis due to mutation in the CFTR gene. CFTR is the protein that releases chloride ions into the lumen.
Cystic fibrous: describe what the mutation is, what this means and the symptoms
Tissues that have mucins and cilia are all affected, this is because the CFTR mutated gene, is important in the release of chloride ions in the lumen. As less chloride ions enter the lumen, less water enters the lumen, making the mucus very sticky.
Symptoms:
- Airways: clogging and infection due to thick sticky mucus (mucus can’t move out into oral cavity as easily. The thick sticky mucus also obstructs breathing and progressively damages the lungs.
- Liver: small bile duct becomes blocked
- Skin: malfunctioning of sweat glands, results in very salty sweat and crystals on the surface of the skin (not as many chlorides out in the skin, so not enough water moving out, so ions are very concentrated)
Clara (club) cells: where are they located, what do they look like, what are their functions
Found in the airway side of the terminal bronchioles
Have a club like apical surface
No cilia and no basal bodies
Functions:
- Detoxify harmful substances inhaled by the lungs
- Acts as stem cells: Multiply and differentiated into ciliated cells to regenerate the bronchiolar epithelium
Microfold cells: location, function, disadvantage
Look like a mushroom cap
Function:
Important in the immune system
- Traps pathogens and other molecules
- Present to underlying dendritic cells that process material (e.g. pathogens)
- Dendritic cells then presents this harmful substance to lymphocytes and macrophages (the lymphocytes and macrophages ‘reside’ in the basal ‘pocket’ (the basal pocket is not linked to the basement membrane).
Disadvantages of M cells (microfold cells) -
They are very important for immune response, but also represent a weak point in the intestinal epithelium, many pathogens exploit them as a portal of entry
Location: Found only in the small intestine (near lymph nodes)
Stereocilia: location
In the inner ear: Mechanosensing organelles of hair cells (sense movement within the inner ear), respond to fluid motion for hearing and balance, they vibrate and send a signal to a neurone)
In the epididymis and vas deferens: Stereocilia facilitate absorption of the residual sperm body after spermiation has completed. Science not sure yet - but could be involved in sperm movement along the ejaculatory ducts.
Cell renewal rates and smoking (affect on the airway epithelium). Early stage of lung damage -
Normal mucus layer thickens
Cilia die off
Ciliagenesis (cilia regrow after 2-4 days)
Cell renewal rates and smoking (affect on the airway epithelium). Chronic stage of lung damage -
Goblet cells and basal cells proliferate (multiply)
Club cells change shape or die (do not regrow)
Fibroblasts lay down scar tissue (epithelial cells then find it hard to repopulate over scar tissue)
Smoke contains carcinogen that induces mutations and malignancy
Pneumocytes in the alveoli die
List some common respiratory conditions related to smoking
- Acute bronchitis
- Chronic bronchitis
- Emphysema
- COPD
- Asthma
Acute bronchitis
Cough and mucus production, breathlessness < 3 months
Reduced lung function and breathlessness due to inflammation, swelling and narrowing of the lung airways and excess mucus in the lung passages
Later stage - Increased risk of serious respiratory diseases
Chronic bronchitis
Chronic inflammation of the bronchi and bronchioles that produces a cough and mucus production that has at least 2 episodes of cough lasting 3 months or more during a 2 year period (smoker’s cough)
• Reduced lung function and breathlessness due to inflammation, swelling and narrowing of the lung airways and excess mucus in the lung passages
• Start of or irreparable damage to the bronchioles and alveoli
Emphysema
Damage to air sac, loss of elastic recoil and permanent changes to the size of the alveoli (fuse and enlarge)
COPD (Chronic Obstructive pulmonary disease)
Umbrella condition that includes both emphysema and chronic bronchitis
Asthma
Wheeze, shortness of breath, chest tightness and cough that may vary over time and in intensity, together with variable expiratory airflow limitation (often has a trigger, e.g. cold, exercise, allergens, stress, etc.)
Caused by bronchospasm (tightening of the smooth muscle layer in the bronchi and bronchioles), obstruction from mucus and narrowing of the
conducting airways
