A&P 1 Skeletal Lab Week 1 Pre-lab Guide Skeletal Background Information

Transcription

1 A&P 1 Skeletal Lab Week 1 Pre-lab Guide Skeletal Background Information Note: These notes are very similar to those found in your lecture notes. This info is for BOTH LECTURE AND LAB! Read through them and make sure you understand the concepts after watching the videos. You should take your own notes, and use these to check that you didn t miss anything in your notes! YOU WILL NEED THE IMAGES IN YOUR TEXTBOOK OR LAB BOOK FOR THIS LAB! Our lecture book has an excellent section on the skeleton, including summary tables. Of course, there are usually extra textbooks in lab! Take a look at the Wordlist for this lab. Notice that it shows you what features to know off of which bones! I also have some links on the website to some online resources that may help, but these are not mandatory. You will be doing work on your own, in the Learning Lab. This is mandatory! There is a special section of videos on the website for you to use in the Learning Lab. Referring to our lab manual Anatomy & Physiology 1 by Chuck Benton Old version: ISBN New version: ISBN These chapters & exercises refer to the old version : Before coming to lab Chapter 5: Introduction to the Skeletal System, the following sections: Division if the Skeletal System Major Bones of the Body Bone Features In Learning Lab (on own time): Chapter 5: Introduction to the Skeletal System, the following sections: Composition of Bone Bone Morphology (Regions of a long bone) Bone Classification Microscopic Structure of Bone In-Lab Activities: First you should work on the skull, using: Exercise 11 Axial Skeleton - Skull Then, work on the vertebral column and thorax, using: Exercise 10 Axial Skeleton - Vertebrae, Ribs, Sternum, Hyoid

2 Skeletal Lab Week 1, Video Series #1 Intro to Lab Video #1: Intro & Functions of the Skeleton I. The Skeletal System You should be ready to ID the bones and bony features in lab, although you may have to know generalities about the skeleton in lecture. A. Overview of Bones and Skeletal Features - Skeleton: * The skeleton (From Greek skeletos = "dried-body", like a mummy) * forms the supporting structure of the body. - Functions of the skeleton: 1. Support & framework for organs. * muscles attach to bones via tendons, causing movement around joints. 2. Protection (e.g.: skull protects brain, vertebrae protects spinal cord, ribs protect thoracic cavity). 3. Movement-muscles cause bones to move around joints, causing movement. 4. Mineral storage - especially calcium phosphate, which must be occasionally released into the bloodstream for use by the body s cells. 5. Blood cell formation - hematopoietic tissue = red marrow. - Bones in a typical adult: * There are, in an average adult, 206 bones in the skeleton. ** this changes through life, as bones fuse ** also, we differ in the number of Sesamoid and Sutural bones. - The musculoskeletal system: Muscles cause movement around joints or articulations. * muscles attach to bones via tendons. * at a joint, one bone will be moved with respect to another. Sometimes towards, sometimes away from, sometime around. ** the other bone is "fixed" or held still.

3 Skeletal Lab Week 1, Welcome Series Video #2: Function Regions of the Skeleton Axial vs. Appendicular - The skeleton can be subdivided into 2 skeletons, which differ in what they protect and support: Axial Skeleton: Protection is key! Appendicular Skeleton: Movement is key! 1. Axial Skeleton: Protection is key! Does all of the functions mentioned above. But, crucially, it surrounds & protects particularly fragile organs: the CNS, lungs and heart. Surrounds the dorsal cavity and the thoracic cavity. * Due to the vulnerability of the CNS, this portion of the axial skeleton is "tightly sealed", with less spaces available for the joints. Much less movement. * On the other hand, the heart and lungs must expand. This portion of the axial skeleton has more movement: the thorax, including the ribs. It is not entirely bone, and there is a lot of cartilage in this region. * Further subdivided: (a) Cranium - surrounds the brain within the cranium. (b) Vertebral column - surround the spinal cord within the vertebral canal or cavity. (c) Bony thorax, or Thoracic cage. 2. Appendicular Skeleton: Movement is key! - It provides the bones and articulations for locomotion (movement through space). - 2 girdles, + their associated limb bones: (a) Pectoral girdle, with arm bones "Pectoral" refers to the chest region. Attaches to the axial via the shoulder. (b) Pelvic girdle, with leg bones. "Pelvis" is the Latin word for a "basin"

4 Skeletal Lab Week 1, Video Series #2: Features of Bones (6 videos) - Bones have identifiable features that aid them in this task. ** These features can be classified in 3 main categories. We'll have a fourth category for "other specialty terms": 1. Bumps (Projections): Process (processes) Process: general term. Some are simple named "such-and-such process". However, there are several types of processes, and sometimes more specific terminology is used. Please remember all of these terms refer to a type of process. There are 2 main reasons for a bump: (i) Modifications for an articulation: Condyle: A rounded projection, modified for an articulation. Head: An elongated condyle, that sits on a narrow structure called a "neck". Facet: flat articular surface, like the facets on a diamond. (ii) Projections designed for muscle attachments: Tubercle: relatively small, rough processes. Tuberosity: larger, raised rough. Trochanter: Even larger, and projects outward. Humans only have them on the femur. Crest: An elevated ridge, usually very rough (big muscles attach). Epicondyle: Bump sticking off of a condyle. Notice the condyle is smooth and part of the joint, while the epicondyle is rough, and projects outward. Spine: Narrow, elongated ridge of bone 2. Depressions or grooves: Fossa (e) 2 main reasons for a groove... (the same 2 reasons cited for processes): (i) Modification for a joint (ii) Often give surface area for muscle attachments Fossa: general term. Most are simple named "such-and-such fossa". Notch: deeper Groove: elongated. Also sometimes called a "sulcus".

5 3. Holes: Foramen(a): an opening for something to pass through the bone, such as blood vessels, nerves, etc. Not as diverse as processes; most are simply called the "such-and-such foramen". There are 3 special cases: Sinus: an opening completely encased in bone. You can't see them unless you cut into the bone. Meatus, or Canal: a tunnel through thick bone. Alveolus: a socket, like the tooth socket. 4. Other "Specialty" Terms: Suture: A special kind of joint between large flat bones. Often fused, so you can no longer see the boundary. Skull, hip. * The os coxae, or hip bone, is actually 3 bones, but you cannot see where they start & stop on most adults. Fontanelle: soft spot on a baby's skull. This is where intramembranous ossification is not finished within the womb, so the skull would have some flexibility during childbirth and later, during brain growth.

6 Skeletal Lab Week 1, Video Series #3: The Axial Skeleton, and an intro to the Skull The Skull (i) Functional Regions - The skull can be subdivided into 2 functional regions: 1. The Cranium, which surrounds the cranial cavity, housing the brain within the cranial vault. - The brain is very delicate; it cannot repair itself very readily if damaged. Also, it must be constantly bathed in Cerebrospinal Fluid (CSF), which provides nutrients. If CSF is lost, the tissue dies very rapidly. Cranium is completely surrounded by bone, with very little exposure to outside world. The bones are tightly articulated, with little movement. This part is fairly round and smooth on the outside, as not many muscles attach here. However, there are a lot of features inside the cranial vault for the brain. 2. The Facial Bones, where we see accommodations for 3 large, obvious structures: the eyes, the nose, & the mouth. This part of the skull has a lot of projections for muscle attachments to accommodate chewing, swallowing and facial expressions. Much more movement. - The bones of the skull can usually be identified by obvious sutures. * A special type of articulation. (Non-movable joints primary function is protection not movement) In life, there would be a thin piece of fibrous membrane. * Sometimes, sutures fuse, especially as we age. They may be lost on the skull you look at. However, some major ones that are usually present are valuable landmarks: 1. Sagittal suture - divides the top sagittally. 2. Coronal suture - "coronal" refers to crown; this is where a crown would sit. 3. Squamous (Squamosal) suture - "flattened, like a scale" 4. Lambdoid (Lambdoidal) suture - shaped like the Greek lambda (λ)

7 * Some sutures are very "loose" and represent weak points in the skull. Brain is surrounded by a fluid: Cerebrospinal fluid. Brain must be bathed in this fluid. If break the sutures, easy at the inferior portion, fluid leaks out. - There are several important regions of the skull, composed of several bones, which will often be referred to: 1. skull cap ("calvaria") 2. base * Sometimes the floor" is synonymous, sometimes used to refer to the inner base * Notice the cranial fossa, which are basins that accommodate the brain.

8 3. orbital region, or orbits 4. nasal region, or cavity * has a septum, or wall, between the 2 sides. (septum composed of bone and cartilage) 5. oral region or cavity, with a hard palate: floor of the nasal cavity, roof of the oral cavity. * in life, there would be a soft palate made of connective tissue and muscle behind the hard palate, finishing the division. 6. There are also sinuses, or open spaces found within several of the bones. * These cannot be seen from the outside. * Paranasal sinuses: a series of sinuses that surround the nasal cavity. Named after the bone they are found within. Help to lighten the skull, and help in immunity. ** Since they are named for the bones they are found within, we will save this discussion for later.

9 Skeletal Lab Week 1, Video Series #4: "Other Bones" associated with the skull - This is our category for bones & features that did not fit nicely into another category. 1. Paranasal sinuses. - Air-filled chambers. - Named after the bone they are found in: Frontal, sphenoid, ethmoid, maxillary - Enclosed by bone. Cannot see on an intact skull. If skullcap is cut, can often see part of the frontal sinus. - Lighten the skull & help warm & humidify incoming air. - Lined with a mucous membrane. Sinuses drain into nasal cavity via small ducts. 2. Hyoid bone. * Sinus infection: Upper respiratory track infection can cause inflammation, lack of drainage. Pathogens infect sinus cavities. Unfortunately, can pass through bone, end up in mastoid sinus near the CNS. If unchecked, can lead to meningitis or encephalitis (inflammation of brain coverings or brain tissue itself). - Slender, U-shaped bone. Hyoid = "shaped like a U" - Does not directly articulate with another bone. - Larynx (voice box) suspended from hyoid; mandible & tongue muscles attach. 3. Auditory ossicles. - Small bones embedded in Temporal bone. * Cannot see from outside. * Function in hearing. Will do more detail in "Ear, Hearing and Equilibrium" module.

10 Skeletal Lab Week 1, Video Series #4: Vertebral Column & Thoracic Cage The Vertebral Column & Bony Thorax (or thoracic cage) - We will talk about these as a unit. (i) Structure of the vertebral column - House & protect the spinal cord * Spinal cord, like the brain, is very delicate, and must be completely surrounded by CSF. * However, the column runs down the back, which needs more movement than what is afforded by the cranium. * Vertebral column = series of smaller, disc-shaped interlocking bones, called vertebrae, with spongy fibrocartilage pads between them called intervertebral discs. These pads act as shock absorbers and allow the back to move. ** These interlocking bones provide quite a bit more movement than if the spinal cord were housed in a solid tube. Notice that the vertebral column gives up stability for flexibility. * The individual vertebrae have a central foramen. So, when they interlock, we end up with a hollow channel running the length of this flexible tube. ** The tube is continuous with the foramen magnum of the skull, so the spinal cord can directly connect to the brain. ** This tube is also filled with CSF, bathing the spinal cord in this necessary fluid.

11 * Also, interlocking vertebrae form a foramen between them (intervertebral foramina) that allow nerves to enter & leave the spinal cord. * The individual vertebrae also exhibit processes for muscle attachments, as well as rib attachment (in the case of the vertebrae behind the thoracic cavity). * There are special joints on the anterior end of the vertebral column that allow movement of the head. - The vertebral column is not straight; that would lead problems with holding up weight and maintaining balance. * A spring-like "S" shape is better at holding up weight while allowing flexibility. * Also, allows us to maintain a center of gravity directly over our legs.

12 - The Spinal Curvatures: The "S" shaped column has 4 curves, each of which defines a region of the vertebral column: 1. Cervical curvature: neck vertebrae. There are 7 cervical vertebrae, C1 - C7. The superior-most articulate with the skull. The skull needs to rotate, elevate and depress. Therefore, we have 2 very special cervical vertebrae forming a special joint: the atlas (C1) and the axis (C2). We will ID them specifically in an upcoming section, called "Discerning the types of vertebrae, the atlas and the axis". 2. Thoracic curvature: behind the rib cage. There are 12 thoracic vertebrae, T1 - T12. Articulate with ribs. 3. Lumbar curvature: Lower back. There are 5 lumbar vertebrae, L1 - L5. Main weight- bearing vertebrae. 4. Pelvic curvature: Fused vertebrae allow the pelvic girdle to attach in a solid manner. Structures are called the sacrum and a coccyx. (ii) Structure of the Vertebrae, Sacrum & Coccyx - This structure results in a total of 26 individual movable parts in an adult - 24 vertebrae, 1 sacrum, & 1 coccyx. * Recall that the vertebral column give up some stability for increased flexibility. This is done by forming the column from 24 interlocking pieces.

13 2. Distinguishing the types of vertebrae, the axis and the atlas - The vertebrae of a specific region differ in structure and shape from those from a different region, and can be identified. * Cervical vertebrae: Only vertebrae with transverse foramen (foramen in the transverse process). The skull have blood vessels and nerves entering & leaving the foramina at the base of the skull. The cervical vertebrae must accommodate this; lower vertebrae do not because the vessels & nerves have moved out away from the spine by then. Some also have a bifid spinous process ("split in two"). * Thoracic vertebrae: only vertebrae with an articulation for the rib on the transverse process and body. These can be difficult to see, however. Also note the long pointed spinous process that points inferiorly (downward) * Lumbar vertebrae: Large, heavy body up to 1/2 of the overall size. Square, stubby transverse process.

14 3. The Sacrum - Large, wedge-shaped with 5 (usually) fused vertebrae. Why "usually"? Sometimes, we see "Sacralization of lumbar". Conversely, we sometimes see "transitional vertebrae" - un-fused sacral. - Superior articulating facets articulate with L5. - Sacral Foramen allow nerves to enter / leave the spinal cord. 4. The Coccyx - Terminal portion of the vertebral column. "Tailbone". - Usually 4 fused vertebrae.

15 (iii) The Thorax - Thoracic vertebrae in back, with a sternum and ribs. 1. Sternum - 3 fused bones: * manubrium * body * xiphoid process 2. Ribs (costae) - Bones that form a cage, housing heart & lungs (and other organs up in this area). Give protection, but allow expansion & contraction, which the heart & lungs need pairs. - Parts we will look at: * head: articulates with the vertebrae. * neck: constriction just below head. * tubercle: process near the neck, that articulates with the transverse process of the vertebrae.

16 - Ribs are classified based on how they connect to the sternum (i) "True ribs" - vertebrosternal - connect directly to sternum. Pairs 1-7 Individually joined to sternum by large piece of hyaline cartilage. (ii) "False ribs" - no direct connection to sternum. 2 types: * vertebrochondral - join to sternum via a single shared piece of cartilage. Pairs 8-10 * vertebral ribs ("floating") - not articulated with the sternum at all. Pairs 11 & 12

17 (iv) Vertebral Deformations & other pathologies 1. The discs themselves are open to problems. Herniated disc: Disc anatomy includes a tough outer fibrous shell of the fibrocartilage pad, called the Annulus ("ring"), and a soft center Nucleus Pulposus. Herniated disc = Annulus tears, allowing the soft Pulposus to squeeze out and press on nerves and perhaps even the spinal cord itself. 2. Abnormal spinal curvatures: SCOLIOSIS is a lateral curvature, usually in the thoracic region. Most severe cases result in unequal limb length & muscular paralysis. KYPHOSIS is a dorsally exaggerated thoracic curve (hunchback). Can be caused by osteoporosis in elderly patients. LORDOSIS (SWAYBACK) is an accentuated lumbar curve. Often caused by rickets or spinal tuberculosis. Also common in pregnant females, potbellies, etc.