Squamous epithelium, ciliated epithelium and cartilage are tissues found in healthy humans.
Which one of the following structures is made up of at least TWO of these tissues?
A. alveoli
B. oviduct
C. Bowman’s capsule
D. trachea
E. capillaries
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Remember that the main types of epithelium are squamous, cuboidal, or columnar. These can then be further divided into simple or squamous, and they can also be keratinized. There are 7 main types of connective tissue: loose connective tissue, adipose tissue, dense fibrous connective tissue (ex. ligaments and tendons), elastic connective tissue, cartilage, osseous tissue (bone), and blood.
Epithelium types:
Squamous: Thin layered cells that allow for easy diffusion. Found in endothelium and lining blood vessels and organs. Also found in areas of high abrasion (ex. skin = stratified squamous epithelium).
Cuboidal: secretory, often found in ducts or glands, also line kidney tubules.
Columnar: tall cells that play a role in protection and absorption of nutrients, for example lining the GI tract.
Simple: single layer of these cells, often found on areas of high diffusion (ex. alveoli)
Stratified: layers - more common in areas subject to abrasion (friction, for example, lining the alimentary tract.
Pseudo: false. so if you see pseudostratified it means false layered. False layered cells are when there are nuclei at varying heights which gives the appearance of multiple layers even when there are not (seen in columnar cells).
Keratinized: Keratin layer provides further protection ex. skin
Ciliated epithelium: this is not a distinct type on its own like columnar, cuboidal or squamous, it is a characteristic of cells. Not all epithelium can be ciliated, it is most commonly columnar, but also note that not all columnar has to be ciliated.
Now onto cartilage:
Cartilage is a connective tissue that plays a role in protection, providing a strong yet flexible structure. It is important to know that there are cartilage rings that help keep the trachea’s shape.
Note: focus on the kind of tissues found in the organs and systems of interest (ex. GI, urinary, etc…)
Now let’s look at the answers:
A. alveoli - contains simple squamous epithelium to allow for easy gas exchange in the lungs but the ciliated epithelium of the respiratory system stops at the level of the bronchioles. Therefore A is incorrect.
B. oviduct - part of the genital tract. Consists of smooth muscle, mucosa lining, the columnar epithelium (ciliated) etc… the only relevant tissue from this question they contain is the ciliated epithelium.
C. Bowman’s capsule - This is a place of high diffusion and absorption of nutrients. Here we can find only squamous epithelium, therefore C is incorrect.
D. trachea - the trachea is a part of the respiratory system and is BEFORE the bronchioles, so we know there must be some ciliated epithelium here. There are also cartilage rings providing support to our trachea. Therefore D is correct.
E. capillaries - are made of the endothelium (simple squamous epithelium) to allow for the diffusion of nutrients. It does not contain the other tissues therefore E is incorrect.
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