can be seen as a yellowish layer beneath the skin (postmortem), surrounding organs, etc., which act as a covering or protection to them; it has a wide distribution and is never found in the ear, eyelid, or genitalia (male), and is always found back of the eye-ball and in the kidney, no matter how poorly nourished an individual may be, even to the extent of starvation. 7. Lymphoid Tissue. — This is made up of a network of reticulum, holding among its fibers the white blood cells or leukocytes. The cells seen are mostly small lymphocytes, and some large lymphocytes and poly-nuclear cells. (See blood, page 221.) There are three varieties of lymphoid tissue: (a) diffuse; (b) solitary follicles; (c) Peyer's patches; and lymph nodes. (a) The diffuse variety is found in the tunica propria of the mucous membrane of the alimentary and respiratory tracts, the medulla of the thymus body, and the greater portion of the tonsil and spleen. (b) Solitary follicles are found in the alimentary and respiratory tracts, spleen, and tonsils. (c) Peyer's patches consist of a collection of solitary follicles clearly outlined from the surrounding tissue. They are found in the wall of the ileum (the terminal portion of small intestines which opens into the cecum). Lymph nodes (glands). (See Lymphatic System.) 8. Cartilage. — Cartilage is not as compact or strong as bone. It is more yielding; thus it will be found in different parts of the body when this firm yet pliable property is essential to the function of an organ. We see it in the cartilages of the larynx, where one may readily understand how its structure must be more or less elastic owing to the constant action of the muscles upon the cartilages and their change in relationship during talking, singing, etc., and its value can be appreciated when placed between bones, as a shock absorber; demonstrated by the intervertebral disks between each vertebra. In studying the structures of cartilage it is considered under perichondrium, cells, and intercellular substance. The perichondrium is a fibrous sheath which surrounds cartilage and corresponds to the periosteum of bone. It is divided into an outer fibrous layer containing few cells, and an inner portion or chondrogenetic layer, consisting of flattened and elongated or spindle-shaped cells. These are the chondroblasts or cartilage cells. The latter cells are seen just beneath the perichondrium, where they appear as flat cells, then as the center of the cartilage is reached they become more oval or even round. Each cell is rich in protoplasm and contains one or more vacuoles. The cell is surrounded by a capsule, and a small space intervenes, between the cell and the capsule called a lacuna. The intercellular substance consists of a homogeneous mass in the hyaline cartilage, and of white fibrous and yellow elastic fibers, in the white fibrocartilage and yellow fibrocartilage respectively. There are three varieties of cartilage: Hyaline, white fibrocartilage, and yellow fibro or elastic. The hyaline cartilage is pearl blue in color, is elastic, and cuts with a knife. It is found in the body covering articular surfaces of bones, which line joint-cavities; in costal cartilages as found between the ribs and breast bone or sternum; in cartilages surrounding the trachea (windpipe); and in most of the laryngeal cartilages. It may ossify in old age. The white fibrocartilage is not very plentiful and acts as a structure to deepen joint-cavities, as interarticular fibrocartilages and intervertebral disks. Yellow fibrocartilage is found wherever elasticity is required, as in the epiglottis. Eustachian tube, ear, and smaller laryngeal cartilages. It never ossifies. Cartilages are very poorly nourished, as they do not contain many bloodvessels, except in the perichondrium; and except when the cartilage is developing. No lymph channels are present. Note. — Muscle, osseous, and nerve tissues are described under the chapters on Muscles, Bones, and Nerves respectively. QUESTIONS 1. What do you understand by the term maturation? Fertilization? 2. What three layers of cells are developed from the ovum after maturation and fertilization are completed? 3. What are the tissues of the body divided into? 4. Name the functions of epithelial tissue. 5. In what cavities of the body are epithelial cells found? 6. Give the classification of epithelial cells. 7. How do ciliated cells differ from other cells? 8. What is characteristic of stratified cells? 9. In which direction do the motion possessed by ciliated cells point? 10. What layers of tissues enter into the formation of a normal mucous membrane? 11. Which layer contains bloodvessels, lymphatic spaces, nerves, glands, and lymphoid tissue in certain organs? 12. Which layer contains involuntary non-striated muscle tissue? 13. Give the subdivisions of glands. 14. What are the three varieties of secretions from glands? 15. How do serous membranes differ from mucous membranes? 16. What name is given to the type of cells covering the serous membranes? 17. Where are serous membranes found throughout the body?
Key Takeaways
- Lymphoid tissue is composed of reticulum and white blood cells, with three varieties: diffuse, solitary follicles, and Peyer's patches.
- Cartilage is less strong than bone but more flexible, found in the larynx and intervertebral disks as shock absorbers.
- There are three types of cartilage: hyaline, white fibrocartilage, and yellow fibrocartilage.
Practical Tips
- Understand the distribution and function of lymphoid tissue to identify potential sources of infection or immune response in survival scenarios.
- Recognize the importance of cartilage as a shock absorber in joints and other areas, which can be critical for maintaining mobility during extended periods of physical activity.
- Identify serous membranes' locations and their protective role, such as covering organs to prevent friction.
Warnings & Risks
- Be cautious when handling tissues that contain lymphoid cells or cartilage, as they may have specific functions in the body's defense mechanisms.
- Avoid damaging cartilaginous structures, especially those found between bones, as this can lead to long-term health issues.
Modern Application
The knowledge of lymphoid tissue and cartilage is still relevant for modern survival preparedness. Understanding these tissues helps in recognizing signs of infection or injury, which are crucial during emergencies. While the chapter's focus on specific cell types may not be as directly applicable today, the principles of tissue function and distribution remain essential for medical triage and basic first aid.
Frequently Asked Questions
Q: What are the three varieties of cartilage mentioned in this chapter?
The three varieties of cartilage mentioned are hyaline, white fibrocartilage, and yellow fibro or elastic cartilage. Hyaline cartilage is found in articular surfaces of bones, costal cartilages, trachea, and laryngeal cartilages, while the other two types are found where elasticity is required.
Q: Where can Peyer's patches be found?
Peyer's patches are found in the wall of the ileum (the terminal portion of the small intestine that opens into the cecum).
Q: What is the function of cartilage, and where is it commonly found?
Cartilage serves as a flexible yet firm structure essential for certain organ functions. It is commonly found in the larynx, intervertebral disks between vertebrae, and other areas requiring shock absorption or flexibility.