Epithelial Tissues Flashcards
What are mucous membranes?
They line internal tube which open to the exterior and contain mucous secreting cells
E.g. Respiratory tract, urinary tract, Alimentary tract
Mucous membranes consist of what two layers?
Epithelium (attattched to basement membrane)
Lamina propria - adjacent connective tissue
In the alimentary tract there is a third layer of the mucous membrane, called?
Muscularis mucosae - smooth muscle cell layer
What two things are often present in the connective tissue of the lamina propria?
Peyers patches - aggregations of lymphocytes
Mucosal glands
What are serous membranes?
Thin two part membranes that line certain closed body cavities - envelope the viscera and secrete lubricating fluid that promotes relatively friction free movements of the structures they surround
Give three examples of serous membranes
Peritoneum - envelopes abdominal organs
Pleural sacs - envelope lungs
Pericardial sacs - envelopes heart
What are the outer and inner walls of the serous membrane called?
Outer - parietal serosa
Inner - visceral serosa
What does simple epithelia mean?
One cell thick
What s stratified epithelium?
More than one cell thick
What are the two main functions of the basement membrane?
Serves as a strong flexible layer for epithelial cell adhesion
Acts as a molecular and cellular filter
Name 3 places simple squamous epithelium is seen
Line the glomerulus and bow and capsule
Lines the entire circulatory system (called endothelium here)
Lines the serous membranes (called mesothelium here)
What’s the function of simple squamous epithelium?
Allows rapid exchange of nutrients and gases
Allows certain blood cells to enter tissues (active site by pinocytosis)
Name three locations containing simple cuboidal epithelium
Thyroid follicles
Lining small ducts of many exocrine glands
Kidney tubules
Surface of the ovaries
What are some of the functions of simple cuboidal epithelium?
Synthesis and storage or hormones e.g. Thyroxine
Absorption
Secretion
Barrier/covering
Where are simple columnar epithelium found?
Virtually all of the GI tract - stomach to anus
Gallbladder
Large ducts of exocrine glands
Uterus
What are some of the functions of simple columnar epithelium?
Absorption
Secretion
Lubrication
What is pseudostratisfied epithelium?
Looks like more than one layer of cells, but every cell makes contact with the basement membrane
Contains motile cilia and goblet cells
Where is psudostratisfied epithelium found?
Lining of the nasal cavity, trachea and bronchi
Epididymis and ductus deferens
Auditory tube
Large excretory ducts
What are some of the functions of psudostatisfied epithelium?
Secretion and conduit
Absorption
Particle trapping and removal
Where are non-keratinised stratified squamous epithelium located?
Oral cavity Oesophagus Vagina Part of anal canal Surface of cornea
What’s the function of non-keratinised stratified squamous epithelium?
Protection against abrasion
Reduces water loss, but remains moist
What’s the main difference between keratinised and nonkeratinised stratified squamous epithelium?
Keratinised has a dead cell layer on top (Stratum corneum) made up mainly of keratinocytes
Where is keratinised stratified squamous epithelium located?
Skin
Small amount in oral cavity
What are the four layers of skin epidermis?
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
In which epidermis layer does keratinocyte cell division mainly occur?
Stratum basale
What is the main cell of the stratum corneum?
Corneocytes
What is the transit time from keratinocyte to corneocyte?
28-40 days
What are melanocytes and where are they found?
Dendritic cells, occur at intervals along the stratum basale layer of the epidermis
What’s the function of melanocytes?
Produce melanin - main pigment that gives skin its colour. Amount of melanin produced affects skin colour not number of melanocytes.
Melanin provides uv protection - forms caps on the sunny side of the nucleus
What are langerhans cells and where in the epidermis are they found?
Dendritic cells from bone marrow found scattered through the stratum spinosum.
What is the function of langerhans cells in the epidermis?
Have high specialised capacity to present antigens to T cells - mediates immune reactions e.g. Allergic contact dermatitis
What is the function of keratinised stratified squamous epithelium?
Protect against abrasion and physical trauma
Prevents water loss
Prevents microbe penetration
Shields against in damage
What is transitional epithelium?
Surface cell shape varies from columnar/cuboidal to flattened (squamous). Relaxed and stretched states.
Where is transitional epithelium found?
Bladder
Urethra
Renal calyces
What is the function of transitional epithelium?
Distensibility
Protection of underlying tissues from toxic chemicals
What is a gland?
An epithelial cells/collection of cells specialised for secretion
What tissues does CF effect?
Respiratory tract
Pancreas
GI tract
Skin/sweat glands
What is cystic fibrosis caused by?
Malfunction in/absence of the cystic fibrosis transmembrane regulator (CFTR) which is a Cl- channel (Cl- leaves cell through CFTR)
What is the effect of CF on the respiratory tract?
Failure of the CFTR means less Cl- leaves the cell and consequently less water leaves the cells. Therefore mucous is not hydrated, becomes very viscous, difficult to waft. Can lead to serious pulmonary infection.
What is the effect of CF on the GI tract?
Error in CFTR means less Cl- enters cells and therefore less water leaves, causes viscous mucus.
In newborns, can cause meconium ileus - inability to pass first feaces.
In older CF sufferers, leads to constipation and invagination of parts of GI tract.
What is the acinus of a gland?
The secretory unit of many exocrine glands
What are acinar glands?
Branched - like a bunch of grapes (stalks - ducts)
Where are acinar glands located?
Sebaceous glands
Salivary glands
What is a tubular gland?
Not branched - single acinus
Where are tubular glands found?
Intestinal glands
Merocrine sweat glands
What is a merocrine gland?
Secretes by exocytosis - majority of glands
What is an apocrine gland?
Secretes droplets covered in plasmalemma
E.g. Fat droplets in milk from mammary glands
What is a holocrine gland?
Whole cell breaks down for secretion
E.g. Sebaceous glands of skin
What is the effect of CF on skin/sweat glands?
Absense of CFTR of cells lining the sweat glands, poor reabsorption of Cl- therefore sweat rich in chlorine and sodium (can be used as a CF test)
What are the three major salivary glands?
Parotid - serous gland (no mucus secretion)
Submandibular - tubular, mucus secreting
Sublingual
Explain the exocrine and endocrine function of the pancreas
Exocrine - secrets digestive enzymes (acinar cells - have ducts)
Endocrine - islets of langerhans secrete insulin and glucagon into the bloodstream
What is the effect of CF on the pancreas?
Due to failure of the CFTR, pancreatic secretions contain little water and become thickened, may result in blocking of ducts, inflammation and fibrosis.
The gut receives insufficient enzymes resulting in malabsorption of nutrients
What are the 7 main functions of skin?
Protection - from physical/mechanical stresses, UV, pathogens, chemicals etc
Sensation - contains somatic sensory receptors - touch (pressure, pain, heat, light)
Thermal regulation - through radiation and evaporation
Excretion/secretion- excrete eater and waste products to surface
Immunity - langerhans cells in epidermis act as APC. And phagocytes in hypodermis
Endocrine - cells in epidermis produce vit D3 using UV energy (activated to calcitriol in kidneys)
Growth - can expand due to elastic fibres
What is albinism?
Polygenic recessive condition affecting production of melanin. Sufferers have increased risk of UV damage due to little/no production of melanin
What is psoriasis?
A skin condition associated with the overproduction of skin cells which causes flakey, red patches of skin with silvery colour on surface. In psoriasis skin cells are replaced every 3-7 days!
How can you improve the symptoms of psoriasis?
Vitamin B supplements
Strong steroids
What is rubor?
Redness
What is calor?
Heat
What is tumor?
Swelling
What is dolor?
Pain
Where in the skin are melanocytes located?
At intervals in the stratum basale layer of the epidermis
Where in the skin are langerhans cells located?
In the stratum spinulosum of the epidermis
What is the effect of CF on male reproductive system?
Absence of vas deferens, sperm cannot be added to semen, infertility
What disease may dark skinned individuals in a temperature climate suffer from?
Vitamin D deficiency (produced by skin using energy from UV radiation)
Why to lighter skinned individuals have a higher risk of skin cancer in equatorial climates?
Their melanocytes produce less melanin pigment. This pigment forms a cap over the DNA of the skins keratinocytes to protect from UV damage. Less melanin means less protection
What cells are associated with contact dermatitis is skin?
Langerhans cells (phagocytise and antigen presenting cells)
