"Figure 1.1: Tight junctions – two membranes connected with many spot welds in multiple lines. Desmosomes – two membranes with long strands weaving them together. Gap junctions – two membranes with a few spot welds each of which has a pore in the center.\n\nFigure 1.2: A diagram of a section of skin. The bottom layer is the hypodermis and is mostly made up of large circular cells (fatty tissue). The next layer up, and the thickest layer is the dermis. At the bottom of the dermis are blood vessels, lymph vessels, and nerves, all of which run throughout the dermis. Sweat glands are coiled tubes that lead to the surface. Hair follicles are thick vase-shaped structures containing a hair; an oil gland is attached to the hair follicle. The top layer is the epidermis and is made of many layers of flat cells.\n\nFigure 1.3: A spongy-looking surface with tufts of long hairs. Each hair is about 5 μm long; each tuft is about 10 μm in diameter.\n\nFigure 1.4: Figure a is a diagram of a single goblet cell. The cell is tall and slightly hourglass shaped. The bottom of the cell is filled with a nucleus. The top shows the Golgi apparatus (folds of membranes), rough endoplasmic reticulum (folds of membranes with dots), secretory vesicles containing mucin (large bubbles), and microvilli (finger-like projections at the top). Figure b is a micrograph of two goblet cells within a row of epithelial cells. The epithelial cells are rectangular with a large nucleus visible. The goblet cells are thinner and have a clear (uncolored) top.\n\nFigure 1.5: A diagram of a person. An arrow from the eye points to a larger image that shows eyelashes, the eyelid, and tear ducts. An arrow from the abdominal region shows a larger kidney and ureter. An arrow from the groin region shows a larger bladder, including ureter, pelvic floor muscles, and urethra.\n\nFigure 1.6: A micrograph and diagram both show a large hair follicle, a vase-shaped pocket, with a hair projecting out past the epidermis. On the side of the hair follicle is the sebaceous gland, which is a lumpy structure.\n\nFigure 1.7: A diagram outlining the three complement pathways. At the top is the invading pathogen. Two antibodies bind to an antigen on the surface of the pathogen. C1 binds to the antigen-antibody complex. This is labeled the classic pathway. C1 causes C2 and C4 to be cut into two pieces. Parts of C2 and C4 bind together to form C3 convertase. The alternate pathway also leads to C3 convertase but does so directly. C3 convertase then cuts C3 in two and one of these binds to C3"