Holocrine Sebaceous Glands

Sebaceous glands (glandulae sebaceae) are associated with hair follicles. The alveolar glands have a size of approximately 1 mm. They end in the outer root sheath 2. In the skin of a few body parts also occur free sebaceous glands & (not associated with hairs). This figure shows several rounded sacs (alveoli), which are only incompletely separated from each other. Sebaceous glands are multilayered glands without a lumen of their own (cf. Fig. 134). The gland cells die after secretion is...

Adrenal Gland Glandula Suprarenalis

Suprarenalis Glandular Cell

The adrenal gland is enveloped by a fiber-rich connective tissue capsule H. Above it, there is a layer of vascularized loose connective tissue with many adipocytes. The zona glomerulosa 2 is the outermost narrow layer of the cortex. The epithelial cells in this zone have formed round aggregates or nests. The underlying cells are part of the wide zona fasciculata 3. The cells are arranged in lightly stained strands and columns. The zona reticularis 4 follows without demarcation. It is a loose...

Medulla of the Adrenal Gland

The adrenal gland is a richly vascularized organ. There are connections between the vascular networks of the cortex and medulla. Having passed the medullary sinuses, the venous blood accumulates in the throttling veins, which are characterized by irregularly arranged subendothelial longitudinal muscle strands muscle cushions . In some places, very strong underlying muscles may cause the venous walls to bulge into the lumen. The contraction of muscles underneath the tunica intima presumably...

Pineal Gland Epiphysis Cerebri

Acervulus Cerebri

The pineal gland has a conical shape. Its surface is covered by the pia mater. Connective tissue septa J originate at the pia mater and subdivide the parenchyme into incompletely separated lobes of different sizes. The pineal gland consists of pinealocytes modified photoreceptor cells , interstitial cells and glial cells astrocytes . The interstitial cells often form structures in the same way that epithelial cells do. Degeneration of the pineal gland proceeds throughout human life. It leads to...

Unmyelinated Peripheral Nerve

Collagen Fibrils Membrane

Small unmyelinated nerve from the uterine myometrium of a sexually mature woman. Among other structures, the neuropil contains only unmyelinated axons of the central nervous system. In the peripheral nervous system, each individual unmyelinated axon is cradled in Schwann cells peripheral glial cells cf. Figs. 270, 271 . The axons of peripheral unmyelinated nerve fibers have diameters between 0.2 and 2.5 m. They are bedded in Schwann cell invaginations, which look like trenches, grooves or...

Lingual Glands Posterior Lingual Glands

Anterior Lingual Gland

Groups of mucous glands glandulae radices linguae in considerable numbers exist in the area of the lingual root, radix lingua, under the lingual tonsil see Figs. 338, 339 . The clustered mucous glands are not restricted to the tunica mucosa but extend deeper between the muscle fiber bundles. The glandular ducts end in the canals of the lingual follicles. Connective tissue septa trabeculae stained blue and sectioned striated muscle fibers H are present between the glandular lobes. The nuclei...

Sciatic Nerve Myelin

Sciatic Nerve Transverse Section

Longitudinal section of fiber bundles from the sciatic nerve after staining the myelin sheaths black using osmium tetroxide. Periodically, the myelin sheath shows ring-shaped constrictions called Ranvier nodes cf. Figs. 260, 261 . The axon cylinder is only seemingly exposed at the nodes. Electron microscopy shows that, on the contrary, cytolemma processes from neighboring Schwann cells and a basal membrane see Fig. 261 cover it. The lightly stained band at the lower edge of the figure is the...

Extraepithelial Glands Mucous Glands

Myoepithelial Cells Electrom Microscopy

In light microscopy, the cytoplasm of mucous gland cells appears light. Frequently it is structured like a honeycomb. The flattened nuclei are located in the basal cell space see Figs. 130, 378 . As in serous glands, cells from mucous glands produce many secretory granules, which will finally occupy the entire cell body see Fig. 125 . Electron microscopy shows different patterns of density for the mucus droplets. These droplets will fuse with each other, especially in the apical cell region,...

Peripheral Nerve Myelin Sheath

Inner Mesaxon

The myelin sheath is formed from Schwann cell processes. The plasmalemma processes encircle the myelinated nerve fibers. The myelin structure is based on a lipid-protein system membranes , in which lipid and protein lamellae are stacked in concentric layers. The myelin sheath can be stained using osmium tetroxide cf. Figs. 260, 261, 265, 266, 269 . It can also be stained blue-violet with Luxol fast blue. Electron microscopy shows that the myelin sheath is made up of stacked membranes. The...

Sciatic Nerve

Sciatic Nerve Microscope

Peripheral nerves consist of bundles of either myelinated or unmyelinated nerve fibers that are held together by connective tissue. This cross-section shows numerous fibers of a sciatic nerve U enclosed by the perineurium 2 see Fig. 263 . The perineurium is composed of very flat fibrocytes and collagen fibrils. Dense regular connective tissue covers the entire nerve. 1 Fascicle nerve fiber bundle Stain alum hematoxylin magnification x 10 Fiber bundle fascicle from the sciatic nerve nervus...

Adipose Tissue

Sudan Adipose Tissue

There are two types of adipose tissue unilocular white and multilocular brown adipose tissue. Adipose tissue arises from the pluripotent mesenchymal cells and later from cells of the reticular connective tissue, which can produce grape like fatty tissue lobes also. The reticulum cells store fat droplets that will finally coalesce to one large drop. In the process, the cells become rounder. This often creates remarkably large, about 100 im wide, vacuole cells. Their nuclei and cytoplasm are...

Extraepithelial Glands Holocrine Sebaceous Glands

Histology Nervous Tissue

Sebaceous glands consist of bulbous multilayered epithelium cones, termed sebaceous bulbs or sacs, which lack a luminal space cf. Figs. 612, 613 . The neck of the main bulb opens to the hair shaft. The cells inside the bulb grow larger, produce sebum and consequently, change into sebum cells 2. Their nuclei then die apoptosis . In the usual preparations used for teaching purposes, the fat droplets are removed. This leads to more and more vacuoles in the cells at the center. While producing the...

Ergastoplasm Nissl Bodies

Nissl Bodies Cresyl Violet

The cytoplasm of multipolar neurons from the columna anterior of the spinal cord contains a dense distribution of fine or coarse bodies, which can be emphasized by staining with cresyl violet. They are called Nissl bodies or Nissl substance H tigroid bodies , after Franz Nissl 1860-1919 , who discovered them. Electron microscopy identifies groups of polysomes and components of the rough granular endoplasmic reticulum ergastoplasm as the structures that correspond to the Nissl bodies cf. Figs....