TOB Session 2 Flashcards
Define ‘Gland’
An epithelial cell or collection of cells specified for secretion
What are the 4 means of classification of a gland?
Destination of secretion, Method of secretion, Nature of secretion, Structure of gland (DMNS)
What is an exocrine gland?
A gland with ducts
What is an endocrine gland?
A gland without ducts that secretes directly into the bloodstream.
Into what categories can the structure of a gland be classified?
- Unicellular/Multicellular
- Coiled/Branched/Neither
- Tubular/Alveolar/Tubuloalveolar
- Simple/Compound
What is the difference between a simple multicellular gland and a compound multicellular gland?
In simple multicellular glands, the ducts do not branch. However in compound multicellular glands, the ducts do branch.
Name the eight structures into which glands can be classified.
Simple Tubular Simple Coiled Tubular Simple Branched Tubular Simple Alveolar (Acinar) Simple Branched Alveolar (Acinar) Compound Tubular Compound Alveolar Compound Tubuloalveolar
Describe the secretions of a mucous gland.
The secretions contain mucus and are rich in highly glycosylated proteins called mucins.
What colour do mucous glands stain with haemotoxylin and eosin?
They stain poorly due to the mucus.
Describe the secretions of a serous gland.
The secretions are mucus-free and watery.
What colour do serous glands stain with haemotoxylin and eosin?
They stain pink as they are eosinophilic.
Name the three kinds of secretion
Holocrine
Apocrine
Merocrine
(HAM)
Describe merocrine secretion
Membrane bound vesicle approaches cell surface and fuses with plasma membrane. The contents of the vesicle are released in to the extracellular space and the plasma membrane is now slightly larger.
Where does merocrine secretion take place (name 2 locations)?
Salivary Glands, Pancreas
Describe Apocrine secretion
Non-membrane bound structure approaches cell surface and pushes up apical membrane. Thin layer of membrane surrounds structure and pinches off from the cell. The plasma membrane is now smaller.
Where does apocrine secretion take place? (name one location)
Mammary gland
Describe holocrine secretion
In holocrine secretion, the entire cell disintegrates and releases its contents.
Give an example of a gland that secretes via holocrine secretion
Sebaceous gland
What is endocytosis?
The process of engulfing material into the cell. It is the opposite of merocrine secretion (exocytosis)
What is transepithelial transport?
When a molecule is too large to penetrate the membrane so it is shuttled across an epithelial cell. It is endocytosed at one surface, shuttled across via a transport vesicle then exocytosed at the other side.
Describe the appearance of the Golgi apparatus
It is a stack of disc shaped cisternae with one concave side. Discs have budding vesicels at their edges and distal swellings pinch off as migratory vacuoles.
What does the Golgi apparatus do?
It sorts proteins from the rough endoplasmic reticulum into different compartments and adds sugars to proteins and lipids (glycosylation).
Where do the products of glycosylation go?
The majority are released in secretory vesicles but some are retained in the cells as lysosomes and some enter the glycocalyx.
What is glycosylation and why is it important?
When sugars are added onto proteins and lipids to offer complex shapes for interaction in the glycocalyx. Sugars make the molecules more specific and alter communication with neighbouring cells, adhesion to substrates and movement/division.
How is secretion controlled? (4 methods)
Nervous control
Endocrine control
Neuro-endocrine control
Negative feedback chemical mechanism
How is secretion controlled by nervous control?
Sympathetic nervous system stimulates glands to secrete e.g. adrenal medullary cells are stimulated and so release adrenaline
How is secretion controlled by endocrine control?
Hormones stimulate glands to secrete e.g. ACTH stimulates the cortex of the adrenal gland to secrete cortisol
How is secretion controled by neuro-endocrine control?
Nervous cells of the hypothalamus control production of a hormone which stimulates the gland to secrete e.g. hypothalamus stimulates ACTH production which stimulates the cortex to secrete cortisol
How is secretion controlled by negative feedback chemical mechanism?
e.g. t3 and t4 (thyroxine) inhibit TSH synthesis by the pituitary gland
What are the three major salivary glands?
- Parotid (serous)
- Submandibular (mixed)
- Sublingual (mucous)
Why is mucus thick in patients with Cystic Fibrosis?
The ion channel molecule CFTR is not present in the apical membranes of epithelial cells. Therefore chloride ion transport is compromised so water does not leave the epithelium in sufficient quantities to adequately hydrate the mucus.
How does Cystic fibrosis cause meconium ileus?
The mucus in the gastrointestinal tract becomes thick so the newborn will struggle to excrete the faeces.
Why can cystic fibrosis patients suffer from diarrhoea?
The secretions of the exocrine pancreas become thickened so ducts become blocked and the pancreas becomes inflamed. Insufficient lipase being transported to the small intestine results in the faecal excretion of undigested fat.
Where do you find mucous membranes?
Lining internal tubes that open to the exterior. Alimentary tract, Respiratory tract, Urinary tract.
What does a mucous membrane consist of?
An epithelium, a layer of connective tissue called the lamina propria and (in the alimentary tract) a layer of smooth muscle cells called the muscularis mucosae.
Where do you find serous membranes?
Lining closed body cavities such as the peritoneum, pleural sacs, pericardial sacs.
What do serous membranes secrete?
A lubricating fluid which promotes friction-free movement of the structures they surround.
What does a serous membrane consist of?
A serous membrane consists of a simple squamous epithelium and a thin layer of connective tissue.
A serous membrane is a two part membrane with lubricating fluid in the middle. What are the names of the internal and external membranes?
Internal membrane is the visceral serosa. The outside membrane is the parietal serosa.
What are the four layers of the alimentary tract?
- The mucosa (made up of epithelium, lamina propria and muscularis mucosa)
- Submucosa
- Muscularis externa
- Serosa
What does the muscularis externa do?
It creates peristaltic waves to push the food along the alimentary tract.
What is the serosa?
Simple squamous epithelium (the outermost layer)
What is the mesentery?
It is a layer that contains arteries, veins and nerves between the serosa and the connective tissue.
What are peritoneal organs covered in?
Mesothelium
How does the outside of retroperitoneal organs differ from that of peritoneal organs?
They are covered in adventitia (loose connective tissue)
Name the 6 layers that make up the oesophageal lining.
Epithelium (stratified squamous non-keratinised)
Lamina propria (loose connective tissue)
Muscularis mucosa (smooth muscle cells)
Submucosa (connective tissue with mucus-secreting glands)
Muscularis externa (for peristalsis)
Adventitia (thin outermost layer of connective tissue)
Name the 3 layers of the stomach lining.
Gastric mucosa (Secrets enzymes, acid and gastrin) Submucosa Muscularis externa
What are rugae?
Folds in the gastric mucosa forming longitudinal ridges in an empty stomach.
How many layers of smooth muscle are there in the muscularis externa of the stomach? Name them all.
There are three. Oblique, circular and longitudinal.
Name the 3 layers of the lining of the jejunum
Jejunal mucosa, submucosa, muscularis externa.
What are pilicae circulares?
Circular folds omucosa and submucosa that project into the gut lumen.
What kind of epithelium is found in the large intestine?
Simple columnar
Where is the conducting portion of the respiratory tract?
Between the nasal cavity and the bronchioles.
Where is the respiratory portion of the respiratory tract?
Bronchioles to the alveoli
Where would you find c-shaped hyaline cartilage and what is its function?
Around the trachea to prevent trachaeal collapse
What shape is the cartilage in the bronchi?
Crescent shaped but smaller than in the trachea
What are the properties of the alveoli?
90% simple squamous epithelium for gas exchange. 10% simple cuboidal epithelium to produce surfactant. Numerous macrophages are present to phagocytose particles. Alveoli are surrounded by capillaries and elastic fibres.
Where is the trachealis muscle located?
In the fibroelastic membrane of the tracheal wall.
What epithelium would you find in the bladder wall?
Transitional epithelium
What is the shape of the muscularis externa in the urethra?
Long and circular.
