Dermis is mainly connective tissue, is deep to the epidermis, and is vascular * The skin contains collagen (for strength) and elastic (for stretch) fibers. * The skin is thicker on the posterior than the anterior parts of the body; thicker on lateral parts of limbs than medial parts. —Subcutaneous layer (or hypodermis) is deep to dermis, but is not part of skin. It is mainly adipose tissue B. Layers of epidermis (from deepest to superficial) 1. Stratum Basale (= base) a. has stem cells that continuously divide by mitosis
It gives the cell its shape, it is the outer covering of the cell made up from phospho-lipid-protein bi-layer, which allows the materials to enter and to exit. The cell membrane is not one solid piece. It is made of different pieces. Compounds called proteins and phospholipids make up most of the cell membrane. The phospholipids make the basic bag.
The kidney is surrounded by a capsule membrane, each of these membranes are topped by the conical adrenal gland. Both the kidneys and adrenal glands are coated in adipose tissue. Gross anatomy When the kidney is presented in a longitudinal section it displays an outer darker cortex and an inner paler medulla. The composition of the medulla is made up of cone shaped pyramids known as medullay pyramids, the tip of these cones are pointed into the area where the ureter connects the kidney. “The medulla is further divided into numerous sections called the medullary pyramids.”This region is known as the pelvis of the kidney.
The cell membrane surrounds the cytoplasm. Nucleus: The nucleus is the central part of a cell, it is usually darker than the rest of the cell as it absorbs stain quickly. It is usually the largest structure inside the cell. Most cells have a central, single spherical nucleus but there are many variations. The nuclear membrane has a similar structure to the cell membrane but it contains gaps which allow protein to pass through.
These vessels are generously spread throughout the entire body, present in nearly every tissue of the body. These vessels, similar to the circulatory vessels, are composed of smaller lymphatic capillaries that converge to form collecting vessels. These vessels then merge even further to form what is known as a lymphatic trunks, which give rise to the lymphatic ducts. There are two major lymphatic ducts in the body; the right lymphatic duct, which drains the right arm and right side of the trunk, head and neck, and the thoracic duct, which drains the remaining portions of the
Compound Epithelium – this type of epithelial tissue is made to withstand wear and tear. It is composed by several layers of cells which is the reason for the name of the cell. The epithelium may or may not be keratinised which contains a tough, resistant protein called keratin for example skin or unkeratinised which is what the lining of your mouth is made up of. Unstriated muscle – this is the type of muscle which still contains protein filaments but they do not lie in an orderly pattern as with striated muscle. In this type of muscle the fibres are spindle shaped and generally have a central nucleus, and dove-tail into each other.
These types of glands are simple alveolar glands that are found all over the body except for areas likes the palms and soles. They are found to be quite small on the body trunk yet large on areas like the face, neck and upper chest. These glands secrete sebum which is an oily secretion. The central cells of the alveoli accumulate only lipids until they become so engorged that they burst which makes the sebaceous gland a holocrine gland. Sebum is secreted into areas like the hair follicles or the pores on the skin surface.
Exocrine and endocrine epithelial cells are highly vascular. The diagram below shows the types of epithelium and where typical examples of where they can be found. Epithelial tissue can be divided into two groups depending on the number of layers of which it is composes. Epithelial tissue which is only one cell thick is known as simple epithelium. If it is two or more cells thick such as the skin, it is known as stratified epithelium.
Epithelial cells that produce secretions are called gland cells. Individual gland cells are scattered with other cells in an epithelium. In a glandular epithelium, most or all of the cells produce secretions and they are discharged as “exocrine”. Exocrine is discharged onto the surface of the epithelium. “Endocrine” secretions are released into the surround tissue fluid and blood.
The endoplasmic reticulum (ER) is a system of interconnected membranous sacs, channels, or cisternae in the cytoplasm. It has two subtypes: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The RER is a ribbon-like structure surrounding the nucleus near the base of the cell. Its surface appears rough due to the ribosomes attached to its membrane and it is the first organelle into which membranebound or extracellular proteins are inserted. SER lacks ribosomes and participates in lipid synthesis and detoxification.