Epithelial Tissue And Skin Flashcards
Define epithelia
Sheets of contiguous cells lining the internal surfaces and covering the external surface of the body.
What is a mucous membrane? Give an example of where it can be found.
Membrane that bears mucus-secreting cells to varying degrees. Alimentary tract, respiratory tract, reproductive tract.
Outline the structure of a mucus membrane.
- Epithelium
- Lamina propria = connective tissue
- Alimentary tract: muscularis mucosae
What layer of the mucous membrane contains mucosal glands?
Lamina propria
What is a serous membrane?
A thin, 2 part membrane which lines certain closed body cavities. E.g lung pleura, peritoneum, pericardium
What are the components of a serous membrane?
- Simple squamous epithelium which secretes a lubricating fluid.
- Thin layer of CT which attaches the epithelium to adjacent tissues
What are the 2 layers of the serous membrane called?
Visceral and parietal
What is the basement membrane?
A strong, flexible, acellular layer that epithelial cells adhere to. Consists of a basal lamina laid down by epithelial cells.
What type of epithelium is the epidermis?
Simple, squamous keratinised epithelium
What are the 4 layers of the epidermis?
Basal layer, Prickle cell layer, granular layer, stratum corneum (horny layer)
What occurs in the basal layer of the epidermis?
Keratinocyte mitosis, daughter keratinocytes move up to the prickle cell layer.
What occurs in the prickle cell layer?
Terminal differentiation of keratinocytes and they lose their ability to divide.
What occurs in the granular layer?
Keratinocytes lose their plasma membrane and begin differentiating to corneocytes.
What is the horny layer/stratum corneum comprised of?
Layers of flattened corneocytes.
Other than keratinocytes, which cell types are present in the epidermis?
- langerhans cells in the prickle cell layer
2. Melanocyes in the basal layer
What are langerhans cells?
Dendritic cells with an immune function. They are APC’s which present antigens to T cells.
What is the function of melanocytes?
Secrete melanin in their melanosomes which are then released into adjacent keratinocytes in the basal layer.
What is the ion channel affected in cystic fibrosis?
Cystic Fibrosis Transmembrane Regulator (CFTR) channel which is present on the apical membrane of epithelial cells.
What does the CTFR transport?
Chloride ions
What is the result of a CTFR mutation?
Misfolded protein which cannot insert in the apical membrane.
What are 5 systems that are affected by cystic fibrosis?
- Respiratory tract
- GI tract
- Reproductive tract
- Pancreas
- Sweat glands
Lots of the effects of cystic fibrosis are due to alterations in the mucus. Explain this.
The CTFR usually pumps Cl- into the mucus, which means that water will follow and hydrate the mucus. Without this protein, mucus can become too viscous and difficult to clear.
How does cystic fibrosis affect the pancreas?
The exocrine secretions of the pancreas contain too little water and become thickened, blocking the ducts. The gland then becomes inflamed and fibrotic.
How does cystic fibrosis affect the respiratory system?
Viscous mucus is harder to clear, serious pulmonary infection can result.
How does cystic fibrosis affect the skin?
CTFR usually pumps Cl- back into the body from the skin. Without CTFR, less Cl- is reabsorbed and sweat is rich in chloride and sodium ions.
How does cystic fibrosis affect the reproductive system?
Absent vas deferens
Cystic fibrosis can cause constipation in adults and meconium ileus in newborns.True or false?
True
How can you classify exocrine glands by destination of their secretion?
Endocrine - into blood
Exocrine - through ducts
How can you classify exocrine glands by method of secretion?
Holocrine - whole cell breaks down
Merocrine - vesicular exocytosis
Apocrine - secreted droplets covered in plasmolemma
Which organ has both exocrine and endocrine function?
Pancreas! Exocrine - pancreatic juices into duodenum
Endocrine- insulin
What are the 3 major salivary glands?
Submandibular, Sublingual and parotid
Define a ‘gland’.
An epithelial cell or collection of cells that is specialised for secretion.
Give an example of stratified squamous non keratinized epithelium?
Oesophagus, oral cavity, larynx.
Withstands abrasion.
What are the functions of stratified squamous keratinized epithelium?
Skin epidermis. protection against abrasion and physical trauma Prevents water loss Prevents ingress of microbes Shields UV damage
Where is transitional epithelium located?
Bladder
What do the endothelium, bowmans’ capsule, loop of henle and alveoli have in common?
Simple squamous epithelium
Give an example of where simple cuboidal epithelium is found.
Pancreatic duct, thyroid follicles.
Where can pseudostratified epithelium be found?
Upper respiratory tract - trachea + bronchi
What surfaces is psoriasis likely to affect?
Extensor surfaces - e.g elbow
What are functions of the skin?
- protection
- Thermal regulation and insulation
- Excretion and secretion
- Sensation
- immunity
- Endocrine - produce vit D3 in epidermis
- Growth
What type of collagen is in the basal lamina?
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