Spongy bone consists of plates trabeculae and bars of bone adjacent to small, irregular cavities that contain red bone marrow. The canaliculi connect to the adjacent cavities, instead of a central haversian canal, to receive their blood supply.
How does the medulla work? The medulla oblongata helps regulate breathing, heart and blood vessel function, digestion, sneezing, and swallowing. This part of the brain is a center for respiration and circulation. Sensory and motor neurons nerve cells from the forebrain and midbrain travel through the medulla. What happens if medulla is damaged? Damage to the medulla oblongata can result in: Difficulty swallowing.
Loss of gag and cough reflex. What does the pons control? The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture. Why is it called medulla oblongata? Medulla oblongata, also called medulla, the lowest part of the brain and the lowest portion of the brainstem.
The medulla oblongata plays a critical role in transmitting signals between the spinal cord and the higher parts of the brain and in controlling autonomic activities, such as heartbeat and respiration.
What is the difference between medulla and medulla oblongata? The medulla oblongata myelencephalon is the lower half of the brainstem continuous with the spinal cord. The pons part of metencephalon lies between the medulla oblongata and the midbrain.
It contains tracts that carry signals from the cerebrum to the medulla and to the cerebellum. What does medulla mean in medical terms? The walls of the diaphysis are compact bone. The epiphyses, which are wider sections at each end of a long bone, are filled with spongy bone and red marrow.
The epiphyseal plate, a layer of hyaline cartilage, is replaced by osseous tissue as the organ grows in length.
The medullary cavity has a delicate membranous lining called the endosteum. The outer surface of bone, except in regions covered with articular cartilage, is covered with a fibrous membrane called the periosteum. Flat bones consist of two layers of compact bone surrounding a layer of spongy bone. Bone markings depend on the function and location of bones. Articulations are places where two bones meet.
Projections stick out from the surface of the bone and provide attachment points for tendons and ligaments. Holes are openings or depressions in the bones.
Bone matrix consists of collagen fibers and organic ground substance, primarily hydroxyapatite formed from calcium salts. Osteogenic cells develop into osteoblasts. Osteoblasts are cells that make new bone. They become osteocytes, the cells of mature bone, when they get trapped in the matrix.
Osteoclasts engage in bone resorption. Compact bone is dense and composed of osteons, while spongy bone is less dense and made up of trabeculae. Blood vessels and nerves enter the bone through the nutrient foramina to nourish and innervate bones. If the articular cartilage at the end of one of your long bones were to degenerate, what symptoms do you think you would experience? In what ways is the structural makeup of compact and spongy bone well suited to their respective functions? The surface features of bones vary considerably, depending on the function and location in the body.
There are three general classes of bone markings: 1 articulations, 2 projections, and 3 holes. These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation.
A projection is an area of a bone that projects above the surface of the bone. These are the attachment points for tendons and ligaments. In general, their size and shape is an indication of the forces exerted through the attachment to the bone. A hole is an opening or groove in the bone that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points.
Skip to content Learning Objectives By the end of this section, you will be able to: Describe the microscopic and gross anatomical structures of bones Identify the gross anatomical features of a bone Describe the histology of bone tissue, including the function of bone cells and matrix Compare and contrast compact and spongy bone Identify the structures that compose compact and spongy bone Describe how bones are nourished and innervated function?
It is a disorder of the bone remodeling process that begins with overactive osteoclasts. This means more bone is resorbed than is laid down.
The osteoblasts try to compensate but the new bone they lay down is weak and brittle and therefore prone to fracture. External Website Watch this video to see the microscopic features of a bone.
Chapter Review A hollow medullary cavity filled with yellow marrow runs the length of the diaphysis of a long bone. Review Questions. Critical Thinking Questions 1. Solutions Answers for Critical Thinking Questions If the articular cartilage at the end of one of your long bones were to deteriorate, which is actually what happens in osteoarthritis, you would experience joint pain at the end of that bone and limitation of motion at that joint because there would be no cartilage to reduce friction between adjacent bones and there would be no cartilage to act as a shock absorber.
The densely packed concentric rings of matrix in compact bone are ideal for resisting compressive forces, which is the function of compact bone. Therefore, compact bone tissue is prominent in areas of bone at which stresses are applied in only a few directions.
Figure 1. The inner layer of bones consists of spongy bone tissue. The small dark ovals in the osteon represent the living osteocytes. Whereas compact bone tissue forms the outer layer of all bones, spongy bone or cancellous bone forms the inner layer of all bones. Spongy bone tissue does not contain osteons that constitute compact bone tissue.
Instead, it consists of trabeculae , which are lamellae that are arranged as rods or plates. Red bone marrow is found between the trabuculae. Blood vessels within this tissue deliver nutrients to osteocytes and remove waste. The red bone marrow of the femur and the interior of other large bones, such as the ilium, forms blood cells. Figure 2. Trabeculae in spongy bone are arranged such that one side of the bone bears tension and the other withstands compression. Spongy bone reduces the density of bone and allows the ends of long bones to compress as the result of stresses applied to the bone.
Spongy bone is prominent in areas of bones that are not heavily stressed or where stresses arrive from many directions. The epiphyses of bones, such as the neck of the femur, are subject to stress from many directions. Imagine laying a heavy framed picture flat on the floor.
You could hold up one side of the picture with a toothpick if the toothpick was perpendicular to the floor and the picture. Now drill a hole and stick the toothpick into the wall to hang up the picture. In this case, the function of the toothpick is to transmit the downward pressure of the picture to the wall. The force on the picture is straight down to the floor, but the force on the toothpick is both the picture wire pulling down and the bottom of the hole in the wall pushing up.
The toothpick will break off right at the wall. The neck of the femur is horizontal like the toothpick in the wall.
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