BL - Epithelial Tissues And Exocrine Glands Flashcards
What do mucous membranes line?
Certain internal tubes which open to the interior, e.g. alimentary, respiratory, urinary
What does a mucous membrane consist of?
EPITHELIUM lining the lumen of a tube, layer of connective tissue called LAMINA PROPRIA, third layer of smooth muscle cells (only in alimentary tract) called MUSCULARIS MUCOSAE
What are serous membranes?
Thin, two-part membranes which line certain closed body cavities and envelope the viscera.
Why do serous membranes secrete fluid?
It promotes friction free movement of the structures the membrane surrounds.
What does the serous membrane consist of?
A SIMPLE SQUAMOUS EPITHELIUM which secretes fluid and a THIN LAYER OF CONNECTIVE TISSUE which attaches the epithelium to adjacent tissues.
Do serous membranes completely enclose the organs?
No - the organs are surrounded by the membrane but not completely enveloped.
Which is the outer side of the serosa - visceral or parietal?
Parietal is outside, visceral is inside.
What are epithelia?
Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces.
Give an example of an exterior surface with an epithelial lining.
Skin
Give an example of an interior space that opens to the exterior which has an epithelial lining.
Gastrointestinal tract, respiratory tract, genitourinary tract.
Give an example of an interior space which does not open to the exterior which has an epithelial lining.
Pericardial sac, pleural sacs, peritoneum, blood vessels, lymphatic vessels
What is the basement membrane?
Thin, flexible, acellular layer which lies between epithelial cells and connective tissue.
What does the basement membrane do?
It serves as a strong, flexible layer to which epithelial cells adhere, and a cellular/molecular filter.
What does the basement membrane consist of?
Basal lamina laid down by epithelial cells, which is augmented by a variably thick layer of reticular fibrils.
Give a location where a simple squamous epithelium could be found.
Lining of blood and lymph vessels, lining of body cavities, gas exchange epithelium
Give some functions of the simple squamous epithelium.
Lubrication, gas exchange, barrier, active transport
Give some locations of the simple cuboidal epithelium.
Thyroid follicles, small ducts of exocrine glands,
Give some functions of the simple cuboidal epithelium.
Absorption and conduit, secretion
Give some locations of the simple columnar epithelium.
Stomach lining and gastric gland, small intestine and colon.
Give some functions of the simple columnar epithelium.
Absorption, secretion, lubrication, transport.
What is the difference between simple and stratified epithelia?
Simple has one layer of cells while stratified has many layers. Pseudostratified has one layer but appears to have many.
Give a location of pseudostratified epithelia.
Lining of nasal cavity, trachea and bronchi.
Give a function of pseudostratified epithelia.
Secretion and conduit, absorption
Give a location of a stratified squamous non-keratinised epithelium.
Oral cavity, oesophagus, larynx.
Give a function of stratified squamous non-keratinised epithelia.
Protection against abrasion, reduced water loss while remaining moist.
Why does the epidermis of the skin have no blood supply?
Nutrients can diffuse directly into it.
What are the four layers of the epidermis?
Horny layer, granular layer, prickle cell layer, basal layer.
Which layer of the epithelium does keratinocyte mitosis occur in?
The basal layer.
How is the keratin found in the epidermis formed?
Keratinocytes are formed in the basal layer, then move upwards to form the prickle cell layer. They lose the ability to divide here. Keratinocytes synthesise keratins (fibrous proteins).
What happens to keratinocytes in the granular layer?
They lose their plasma membrane and begin differentiating into corneocytes (main cells of stratum corneum).
What are keratohyalin granules made of?
Keratins, other fibrous proteins, enzymes
Give two examples of cross-link proteins found in the granular layer.
Fillaggrin (aggregates keratins), involucrin (corneocyte envelope).
What is the stratum corneum (horny layer) made up of?
Layers of flattened corneocytes. It has a major role in skin barrier function.
What is the transit time of a keratinocyte from the basal layer to the stratum corneum?
28-40 days.
What are melanocytes?
Dendritic cells of neural crest origin which occur at intervals along the basal layer of the epidermis.
What do melanocytes do?
They produce melanin, the main main pigment that gives the skin its colour.
What are Langerhans cells?
Dendritic cells of bone marrow origin scattered throughout the prickle cell layer.
What do Langerhans cells do?
They have a highly specialised capacity to present antigens to T lymphocytes. They also mediate immune reactions.
Give some examples of where you would find stratified squamous keratinised epithelium?
Surface of skin and some in oral cavity.
What are the functions of stratified squamous epithelia?
Protection against abrasion and physical trauma, prevention of water loss and microbial invasion, shields against UV light damage.
What shape are cells in the transitional epithelium?
They vary in shape from columnar/cuboidal to flattened.
Give some locations of transitional epithelium.
Renal calyces, ureters, bladder, urethra.
Give some functions of transitional epithelium.
Distensibility, protection of underlying tissues from toxic chemicals.
What is a gland?
An epithelial cell or collection of cells specialised for secretion.
What is the difference between an endocrine and exocrine gland?
Exocrine = a gland with ducts.
Endocrine = a gland which secretes directly into the bloodstream ("ductless")Give an example of a unicellular exocrine gland.
A goblet cell.
What is meconium ileus?
An inability to pass the first faeces, often occurs in newborns with CF.
What is an acinus?
The secretory unit of many exocrine glands.
Name the five different structures of simple glands.
Simple tubular, simple coiled tubular, simple branched tubular, simple alveolar, simple branched alveolar.
What is merocrine secretion?
Exocytosis - the vast majority of glands function this way.
What is apocrine synthesis?
Secreted droplets covered by plasmalemma, eg fat droplets in milk.
What is holocrine secretion?
The whole cell breaks down, eg sebaceous gland of skin.
Why does the exocrine pancreas often become inflamed in people with cystic fibrosis?
The secretions contain too little water and become thickened, resulting in the ducts becoming blocked.
