L4- Cell specialisations Flashcards
mucous membrane
Line certain internal tubes which open to the exterior:
- GI tract
- Respiratory
- Urinary tact
mucus membranes have varying degrees of
mucus-secreting cells
mucous membranes consist of
- An epithelium lining the lumen of a tube
- An adjacent layer of connective tissue – lamina propria
- A third layer consisting of smooth muscle cells (circular and longitudinal)- muscularis mucosae
- Also carries blood and lymphatic vessels and nerves
serous membranes
Thin, two-part membranes which line some closed body cavities (spaces not open to the exterior) and envelop the viscera.
serous membranes line the (3)
- The peritoneum- envelops abdominal organs
- The pleural sac- envelops the lungs
- The pericardial sac- which envelops the heart
serous membranes secrete
a lubricating fluid that promotes relatively friction- free movement of surrounding structures.
serous membranes consist of
- A simple squamous epithelium (mesothelium) that exudes the water lubricating fluid
- A thin layer of connective tissue that attaches the epithelium to adjacent tissues
- Also carried blood and lymphatic vessels and nerves
embryonic development of serous membranes
During embryonic development the heart, lungs and gut develop next to a bag-like cavity into which they invaginate
- They each become surrounded by serous membranes that have an inner and outer part
parietal means
outer walls- lines the walls of the cavity
visceral means
inner walls- membranes which covers the organ
epithelia are..
Epithelia are…sheets of continuous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces, including the blood vessels
the epithelium is derived from
all embryological germ layers
ectoderms
forms exoskeleton -epidermis e.g. skin
endoderm
inner and outer lining of GI tract
mesoderm
develops into organs- inner lining of body cavities
endothelium
specialised types of epithelial cells that line interior surfaces of blood vessels and lymphatic vessels
what type of cells are endothelial
simple squamous
types of epithelial cells
- Simple or stratified
o Squamous
o Cuboidal
o Columnar
exterior epithelial surfaces
skin
Interior spaces opening to exterior (mucous membranes)
a. GI tract
b. Respiratory tract
c. Genitourinary tract
Interior spaces which do not open to the exterior
a. Pericardial sac
b. Pleural sacs
c. Peritoneum
d. Blood vessels (endothelium)
e. Lymphatic vessels (endothelium)
simple epithelium
single layer
- squamous
- cupoidal
- columnar
- pseudostratified
stratified epithelium
more than one layer
- squamous
- cuboidal
- columnar
- transitional
epidermis
Surface epithelium of the skin, overlying the dermis
epidermis the the primary site of..
stratified squamous keratinized epithelium
keratinised epithelium is mainly made up of
keratinocytes 9epitheilial cells)
what else is in the keratinised epithelium
melanocytes and langerhas
keratinocytes mitosis
- Occurs in basal layer
- Daughter keratinocytes then move towards the surface differentiating and losing their ability to divide
- Keratinocytes synthesise keratins (fibrous proteins) which contributes to the strengths of the epidermis
normal transit time of keratinocytes from basal layer to stratum corneum
28-40 days
keratinocytes mitosis and psoriasis
- transit time is reduced to 2-4 days- stratum corneum is produced in abundance as silvery scales
number of melanocytes in epidermis
occurs at intervals (1:8 basal layer of epidermis)
melanocytes are hard to histologically without
stains
melanocytes and skin colour
o Mature melanosomes, containing melanin, are transferred to neighbouring keratinocytes by pigment donation, involving phagocytosis of the tips of the dendritic processes
langerhans are also difficult to see
without staisn
role of langerhans
- Highly specialised capacity to present antigens to T lymphocytes
- Mediate immune reactions e.g. allergic contact dermatitis
location of stratified squamous keratinised epithelium
Locations include: skin surface and limited distribution in oral cavity
function of squamous keratinised epithelium
- Protection against abrasion and physical trauma
- Prevention of water loss
- Prevention of microbial ingress
- UV shielding
name some cell surface specialisations
- keratin
- cilia
- goblet cells
- club cells (Clara)
- microfold cells
- sterocilia
- microvilli
keratin
o Prevents water loss and protects against abrasion
E.g. the epidermis (top layer of the skin)
cilia
o Control micro-movement of luminal contents
E.g. in the respiratory system clearing mucus
o Longer and wider than microvilli – movement rather than absorption
o Motile
goblet cells
o Mucus secretions, moistens and lubricates
E.g. in GI, respiratory, urinary systems
club cells (Clara)
o Formally known as Clara cells (protect bronchioles) and acts as stem cells for respiratory epithelium
microfold (M) cells
o Found in the gut, associated with GALT and MALT (gut/ mucosa associated lymphoid tissue
o Delivery of antigens to intracellular immune cells in addition to dendritic cells
stereocilia move at
12Hz
microvilli
increase surface are
what do goblet cells release
muffins through exocytosis
-
deficincency in chloride ion release results in
very stick and immovable mucous e.g. CF due tp mutation inf CFTR gene
gblet cels have
microvilli- no cilia on apical surface
which organs are affected by CF
- airways
- liver
- pancreas
- small intestine
- reproductive tracts
- skin
airways and CF
a. Clogging and infection of bronchial passage with thick sticky mucus obstructs breathing, progressively damages lungs- major cause of mortality in CF patients
liver and CF
a. Small bile duct becomes block, disrupts digestion 5% of CF patients
pancreas and CF
a. Zymogen secretions not released in 85% of pts
small intestine and CF
a. Thick, non-motile stools in 10% of CF neonates- requires surgery
reproductive tracts and CF
a. Absence of fine ducts such as vas deferens renders 95% of CF male infertile
b. Mucus plug in cervix prevents semen transit and reduce female fertility
skin and CF
a. Malfunctioning of sweat glands results in very salty sweat and crystals on the surface of the skin
club cells are found
On the airway side of the terminal bronchioles and have club-like apical surfaces: no cilia or basal bodies.
function of Club cells
- Protect bronchiolar epithelium
- Detoxify harmful substances inhaled into the lungs
- Act as stem cell, multiplying and differentiating into ciliated cells to regenerate the bronchiolar epithelium
how do club cells protect bronchiolar epithelium
o Secrete club cell secretory protein uteroglobulin, and a solution similar in composition to pulmonary surfactant
how do club cells detoxify harmful substances inhaled into the lungs
o Accomplish this with cytochrome p450 enzymes found in their smooth endoplasmic reticulum
microfold cells are a
weak point that can be exploited by pathogens e.g. HIV
structure of microfold cells
- M cells have a folded extension that looks like a mushroom cap that samples the lumen by endocytosis
where are M cells found
only in the small intestine and very close to lymphatic nodule
outline role of M cells
- Traps pathogens and other molecules
- Present to underlying dendritic cells that process material
- Present to lymphocytes and macrophages that reside in basal ‘pocket’ that is not linked to the basement membrane to raise an immune response or digestions, respectively
stereocilia found in the
inner ear, epididymis and vas deferens
stereo cilia and the inner ear
- mechanosensing organelles of hair cells- respond to fluid motion for hearing and balance
sterocilia and epididymis and vas deferens
o Facilitate absorption of the residual sperm body after spermiation has completed
structure of stereocilia
- Stereocilia contain actin and myosin filaments (just like cilia) and so could be involved in sperm movement along these ejaculatory ducts?
smoking
damages the lungs
cell renewal rate of the trachea
1 to 2 months
cell renewal rate of the alveoli
8 days
cell renewal rate of the goblet celsl
10 days
cell renewal rate of the club cells
NEVERRRRR
early stages of damage caused by smoking
o Normal mucus layer thickens
o Cilia die off
o Ciliagenesis- 2 to 4 days
chronic stages of damage caused by smoking
o Goblet cells and basal cells proliferate
o Club cells die
o Carcinogens induce mutations and malignancy
o Pneumocytes in the alveoli
Remaining type II cells proliferate to make type I and II pneumocytes
Fibroblasts lay down scar tissue
acute bronchitis
o Cough and mucus production
o Breathlessness <3 months
Reduced lung function and breathlessness due to inflammation, swelling and narrowing of the lung airways
Excess mucus in lung passages
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 (smokers cough)
emphysema
o Shortness of breath due to permanent widening of airspaces distal to the terminal bronchiole without fibrosis (destruction of the air sacs
COPD
• Umbrella condition includes both emphysema and chronic bronchitis
asthma
- Wheeze, shortness of breath, chest tightness and cough
- Expiratory airflow limitation (trigger e.g. cold, exercise, allergens ad stress)
- Caused by bronchospasm (tightening of the smooth muscle layer in the bronchi and bronchioles, obstruction from mucus and narrowing of the conducting airways)
