TOB: Internal surfaces of the body Flashcards
What is a mucous membrane?
Membrane which line certain internal tubes which OPEN to the exterior
Where can mucous membranes be found?
Alimentary/ GI tract
Respiratory tract
Urinary tract
These mucosal bear mucus-secreting cells to varying degrees
What is a serous membrane?
Thin, two-part membranes which line certain CLOSED body cavities. They envelop the viscera.
Where can serous membranes be found?
Lining the:
Peritoneum
Pleural sacs - envelop the lungs
Pericardial sac - envelops the heart
What layers make up a mucous membrane?
- Epithelium: lining the lumen of the tube
- Lamina propria: an adjacent layer of connective tissue
- Muscularis mucosae (in GI tract only) - a layer of smooth muscle cells (not involved in peristalsis)
What is the function of serous membranes?
They secrete a lubricating fluid which promotes relatively friction-free movement of the structures they surround.
What layers make up a serous membrane?
- Simple squamous epithelium (mesothelioma) which secretes a watery lubricating fluid
- A thin layer of connective tissue which attaches the epithelium to adjacent tissues (also carries blood vessels and nerves) - epithelium don’t have blood vessels
List the four layers of the gut from innermost to outermost
- Mucosa (epithelium, lamina propria and muscularis mucosae)
- Submucosa
- Muscularis externae
- Serosa ((mesothelium) simple squamous epithelium and a thin layer of connective tissue)
In what layer of the gut are Peyer’s patches located?
Lamina propria
What does the submucosa contain?
A layer of connective tissue containing:
Glands, arteries, veins and nerves
How many layers of muscle is there in the muscularis externa of the gut?
Two layers of smooth muscle: outer longitudinal layer and inner circular layer
What is the function of the muscularis externa of the gut?
To create successive peristaltic waves to move luminal contents along the gut
Name the four layers that make up the oesophagus from innermost to outermost
- Mucosa(stratified squamous non-kerratinised epithelium, lamina propria and muscularis mucosae)
- Submucosa
- Muscularis externa (2 layers - inner circular and outer longitudinal)
- Adventitia - thin outermost layer of connective tissue (no peritoneal enfolding of the is portion of the GI tract)
How does the internal surface of the oesophagus differ from that of the gut?
It is not surrounded by serosa (a serous membrane), instead it has a thin covering of connective tissue called the Adventitia
How many layers of muscularis externa does the oesophagus have?
Two: inner circular and outer longitudinal
How does the muscularis externae of the stomach differ from that of the rest of the GI tract?
It has three layers of smooth muscle: oblique, circular and longitudinal.
What are the temporary folds of the stomach called?
Rugae: folds of gastric mucosa forming longitudinal ridges in the empty stomach
What are the permanent folds of mucosa and submucosa present in the small intestine called?
Plicae circulares
Name three ways that the surface area for absorption of the small intestine is increased
- Plicae circulares (folds of mucosa and submucosa)
- Villi
- Microvili
What is the name of the aggregates of lymphoid tissue found in the terminal ileum and colon, which are located in the mucosa and extend into the submucosa?
Peyer’s patches
Name the tubular glands, containing lots of goblet cells, that are found in the colon
Crypts of Lieberkuhn
What is the conducting zone of the respiratory system and what is its function?
The conducting zone is the superior part of the respiratory system and includes the nose, nasopharynx, oropharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles.
Its function is to filter, warm and moisten air and conduct it to the lungs.
What is the respiratory zone of the respiratory system and what is its function?
The respiratory zone is the inferior part of the respiratory system and includes the respiratory bronchioles, alveolar ducts, sacs and alveoli.
Its function is the exchange of gas.
What is the type of C-shaped cartilage that protects the trachea?
Hyaline cartilage
What type of epitheium is found in the trachea?
Pseudostratified cilliated epithelium
Describe the shape of the cartilage found at the trachea and compare it to that found at the bronchi and the bronchioles
At the trachea the cartilage is C-shaped this changes to plates in the bronchi which gradually get smaller until they dissapear when the tube finally reaches about 1mm size, this is when we call them bronchioles.
How does the bronchiole lumen remain open without cartilage?
The surrounding alveoli keep the lumen open. Surrounding elastic fibres attached to surrounding tissue support.
What transition in epithelium is seen as you go down the bronchioles?
The epithelium starts as simple ciliated columnar epithelium and transitions to simple ciliated cuboidal epithelium as the bronchioles decrease in size.
Name the epithelial cells Type 1 and Type 2 in the alveoli and describe their function
Type 1 (squamous) covers 90% of surface area and permits gas exchange with capillaries. Type 2 (cuboidal) covers 10% of surface area and produce surfactant.
What cells are present in large numbers lining the alveolar surface to protect it against foreign agents?
Macrophages
How many cells does oxygen pass through to enter the surrounding capillaries next to the alveoli
Two - first the simple squamous cells of the alveoli and then the simple squamous cell of the blood capillary.
What surrounds the alveoli in a ‘basketwork’?
Capillaries and elastic fibres
Describe the sequence of structures that excreted fluid passes through on its way from the kidneys
Kidney -> Ureter -> bladder -> urethra
What type of epithelium is found in the ureter, bladder and urethra?
Transitional epithelium
How many layers are found in the muscularis externa of the bladder?
Three interwoven layers
How is the bladder adapted to be impermeable to urine?
It has a thick plasma membrane and tight intercellular tight junctions
How does the urethral lumen change shape as urin passes through it?
It goes from stellate to ovoid as urine passes through it
How long is the male urethra?
Approximately 20cm long
How long is the female urethra?
Approximately 3-4cm long
What epithelium is found in the penile urethra?
Very rare stratified columnar epithelium
What is found in the corpus spongin sum of erectile tissue which can appear like artifacts?
Vascular sinusoids
What is the lamina propria?
A thin layer of loose connective tissue, or dense irregular connective tissue, which lies beneath the epithelium and together with the epithelium constitutes the MUCOSA. Therefore this is only found in mucous membranes.
Apart from the lamina propria what other layer is unique to mucous membranes?
Muscularis mucosae
Where is the muscularis mucosae found
GI tract
What is the outermost layer of connective tissue surrounding the trachea called?
Adventitia
