Identify the Tissue or Joint from Its Defining Structure
Animal structure questions give one defining feature and ask for the tissue, muscle band or joint. Learn the feature that distinguishes each, and where each one occurs in the body.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Pseudostratified epithelium
In pseudostratified columnar epithelium all the cells rest on the basement membrane, but some do not reach the free surface, so the nuclei lie at different levels and the tissue appears to have two or three layers without being truly stratified. It is usually ciliated with mucus-secreting goblet cells and lines the trachea, bronchi, vas deferens and epididymis, unlike stratified epithelium (skin epidermis, cornea, anal canal).
Banding of striated muscle
In a sarcomere, the A band is anisotropic and contains the thick myosin filaments (these are the thick ones, about 150 Å), while the I band is isotropic and contains thin actin filaments. A Z line bisects each I band and the sarcomere runs from one Z line to the next. The lighter central region of the A band is the H zone, which has the M line at its middle, so calling it the M zone is wrong. Statements that swap the thick and thin filaments, or give the wrong dimensions, are the incorrect ones.
Joints and the vertebral column
The atlas (first cervical vertebra) turns on the odontoid process (dens) of the axis, a pivot joint that lets the head rotate. Other types are hinge (elbow, knee), ball-and-socket (shoulder, hip), gliding (between carpals) and saddle (thumb). The human vertebral column has about 26 bones, counting the sacrum and coccyx as single fused bones: 7 cervical, 12 thoracic, 5 lumbar, the sacrum and the coccyx; the sacrum joins the hip bones and so is the vertebra related to the pelvic region.
OlympIQ exam lens
- ✓Pseudostratified ciliated epithelium: trachea, vas deferens, epididymis; all cells touch the basement membrane
- ✓A band = thick myosin (anisotropic); I band = thin actin (isotropic); Z line bisects I band
- ✓H zone is the lighter middle of the A band; the M line lies within it
- ✓Atlas-axis joint is a pivot joint around the odontoid process
- ✓The sacrum articulates with the hip bones in the pelvic region
Do not call pseudostratified epithelium stratified. It only looks layered because the nuclei sit at different heights; every cell still touches the basement membrane.
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