Gross anatomy style guide

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Headshot of David Conley, PhD · Clinical Associate Professor, Department of Translational Medicine & Physiology
David Conley
PhD · Clinical Associate Professor, Department of Translational Medicine & Physiology
Office: PBS 41A
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Headshot of Shannon Helbling, PhD · Clinical Assistant Professor, Department of Translational Medicine & Physiology
Shannon Helbling
PhD · Clinical Assistant Professor, Department of Translational Medicine & Physiology
Office: PBS 41C
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Table of Contents

30-min read

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Complete anatomy

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Complete anatomy

Masseter muscle

Chalk Talk

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A note about this session

Note

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Question

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abstract

Abstract text

David Conley

Conley's clues

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Mnemonic

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An important concept

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Image references

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Thought question

If the vermis of the cerebellum were affected, what type of signs could a child exhibit?

FYI

The increased buoyancy of CSF makes a 1500 g brain in air, weigh 50g when floating in CSF.

  • Clinically Oriented Anatomy, 8th ed., Overview of Thorax section through The bottom line: Muscles and neurovasculature of thoracic wall.
  1. Identify the boundaries and contents of the axilla.

  2. Learn the architecture of the brachial plexus.

  3. Identify the muscles, nerves, and vessels of the arm.

The walls surrounding the thoracic cavity are made from layers of muscles and fascia that are reinforced by the thoracic skeleton (“rib cage”). The thoracic wall is cone- shaped; narrower above and wider below. The bones and bulky muscles of the pectoral region, which are properly part of the upper limb, overlie and obscure the relatively small thoracic skeleton, made of ribs, costal cartilages, sternum, and thoracic vertebrae. The spaces between the ribs (intercostal spaces) are filled with muscles, nerves, and vessels. The thoracic wall is flexible and compressible, yet rigid enough to support the upper limb and resist pressures generated within the thoracic cavity.

Gut tube (= inner tube) and its derivatives = air tubes of lungs, liver, gall bladder, and pancreas
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  • From splanchnic mesoderm and endoderm
  • “Visceral” type of innervation from autonomic nervous system
  • Pain from these organs is often referred to somatic body parts.
Body wall (= outer tube)
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  • From somatic mesoderm and ectoderm
  • “Somatic” type of innervation from peripheral nerves
  • Pain from these areas is usually sharp and well-localized.
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Below are links to helpful videos:

    • Development of body cavity.
    • Folding of the embryonic disc.

An organ consisting of an outer layer called the epidermis and a tough connective tissue layer beneath it called the dermis.

The skeletal elements underlying the thoracic body wall consisting of ribs, costal cartilages, the sternum, and thoracic vertebrae.

  • Paravertebral muscles: As the name implies, these are located adjacent to the vertebral column in the back. We won’t be discussing them much in this course, but you should be aware of them, as they form an easily palpable longitudinal mass alongside the vertebral column.
  • Body wall muscles: Three layers in both thoracic and abdominal regions:

    1. External layer
    2. Internal layer
    3. Innermost layer

3.2.4 Review of bones of the thorax.

  • 3.2.1 The bones of the thorax.

  • 3.2.3 First rib and clavicle.

  • 3.2.2 Costovertebral joints. (The ligaments can be skipped.)

  • 3.2.7 Muscles of inspiration. (Just external intercostals; actions are in chapter 7.)

  • 3.2.8 Muscles of expiration. (Just internal intercostals; actions are covered in chapter 7.)

  • 3.2.14 Nerves of the thorax. (Intercostal nerves section only, which is only a few seconds long.)

  • Anatomy is a visual science.

    The best way to learn it is to be able to recall it visually and be able to describe it based on what you see in your “mind’s eye.”

  • Sketch! Sketch! Sketch!

    Do little sketches, flow-charts, or even stick-drawings.

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Draw on me/interactive

(Tap to open; use your Apple Pencil to draw.)

Clinical correlation: extra info

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Clinical correlation

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Clinical correlation

Neural tube defects (NTDs) are congenital anomalies of the central nervous system that result from defective closure of the neural tube during the fourth week.

Because the neural tube fails to close, or is slow to close, NTDs may also influence the tissues surrounding the CNS: meninges,skull, vertebral arches, muscles, and skin. Folic acid deficiency has been linked to NTDs, so pregnant women (and those thinking about becoming pregnant) are advised to take vitamins containing folic acid.

Figure 2.19 LARSEN’ S HUMAN EMBRYOLOGY, 5TH ED., FIG. 4-13. See also Figure 2.20.

A note about this session

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Because the neural tube fails to close, or is slow to close, NTDs may also influence the tissues surrounding the CNS: meninges,skull, vertebral arches, muscles, and skin. Folic acid deficiency has been linked to NTDs, so pregnant women (and those thinking about becoming pregnant) are advised to take vitamins containing folic acid.

Figure 2.19 LARSEN’ S HUMAN EMBRYOLOGY, 5TH ED., FIG. 4-13. See also Figure 2.20.

Question

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Because the neural tube fails to close, or is slow to close, NTDs may also influence the tissues surrounding the CNS: meninges,skull, vertebral arches, muscles, and skin. Folic acid deficiency has been linked to NTDs, so pregnant women (and those thinking about becoming pregnant) are advised to take vitamins containing folic acid.

Figure 2.19 LARSEN’ S HUMAN EMBRYOLOGY, 5TH ED., FIG. 4-13. See also Figure 2.20.

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Embryonic and extraembryonic structures of Week 2. Can you identify these? (tap to open; use your Apple Pencil to draw and make notes)

HAND-DRAWN CONLEY- GRAM.

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The outer layer is the visceral layer of serous pericardium or the epicardium, a serous membrane. It contains a variable amount of fatty tissue deep to the mesothelium.

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The thickest portion of the heart is the middle layer, the myocardium. This layer consists of cardiac muscle tissue.

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The smooth, inner layer of the heart is the endocardium. It is continuous with the endothelium, the simple squamous epithelium lining the blood vessels that enter and leave the heart.

Gestation

The period of intra-uterine development of the human.

Trimester

A period of three calendar months. Clinicians divide the gestation period into three trimesters. The most dramatic and critical stages of development occur during the 1st trimester.

Gestational (menstrual) age

Using the last normal menstrual period as the reference point. Gestation lasts 40 weeks using this calendar.

Fertilization (actual) age

Using the estimated day of fertilization as the reference point. Gestation lasts 38 weeks. In our discussions, we will use fertilization age when describing development.

Embryonic period

The first eight weeks of development. This is a busy time with the most striking advances in development. All of the body’s organ systems have formed by the end of the embryonic period. This period is of most interest to us as we study gross anatomy.

Fetal period

Fetus is the term used to describe the developing human after the completion of the embryonic period. The fetal period therefore is between the ninth week and birth.

Six-pack review

  • Many small branches of nearby arteries—renal, gonadal, and aorta (abdominal part); common/internal iliac and uterine arteries (pelvic part).
  • Anterior: Pubic bones and pubic symphysis. The retropubic space filled with subperitoneal connective tissue is between the bladder and bone.
  • Superior: Peritoneum; vesico-uterine pouch in females.
  • Posterior: Ductus deferentes, seminal vesicles, and rectovesical pouch (male); cervix of uterus and vagina (female).
  • Inferior: Prostate (male); pelvic diaphragm (female).

The empty bladder (rarely the case in the living body) is shaped like an inverted pyramid, and its anatomic parts are described in its empty state. The actual position and shape of the bladder vary according to the amount of urine it contains and the age of the person.

  • Superior surface (dome of the bladder) is covered by peritoneum. The other surfaces of the bladder are subperitoneal.
  • Posterior surface is called the base or fundus of the bladder.
  • Apex of bladder: Connects the bladder to the anterior abdominal wall via a fibrous cord called the median umbilical ligament (urachus).
  • Neck of bladder: Points inferior. This is where urine leaves the bladder and enters the urethra. In the male, the neck rests on the prostate and is fused to it.
  • Figure 20.3 NETTER, ATLAS OF HUMAN ANATOMY, PLATE 313.
    The mucosa of the empty bladder is folded and loose, except in an area at the base called the trigone, where it is smooth and firmly tacked down to the underlying muscle.
  • The trigone is defined by three orifices = two internal ureteric orifices and the internal urethral orifice. The trigone is at the base of the bladder.
  • The trigone may be elevated in males = this is called the uvula of the bladder. It can become quite prominent in older males when the underlying prostate enlarges.
  • The smooth muscle in the bladder wall is called the detrusor (Latin = “to drive away”). It contracts to squeeze out the urine. The detrusor is the juicer! In the neck, smooth muscle forms the involuntary internal urethral sphincter.
  • Ureterovesical junction (UVJ): The ureters pass through the wall of the bladder at an oblique angle. This is the intramural part of the ureter. As the bladder fills and distends, the intramural part closes to prevent backflow of urine from bladder into ureter. This valve mechanism doesn’t work so well in children because the intramural part of the ureter is short and there is not enough bladder musculature. Reflux of urine is a common cause of urinary tract infections in kids.
  • A rest-and-digest function, regulated by parasympathetic innervation. It is under voluntary control but may occur as a reflex involving the micturition center in the brainstem, as in children not “toilet-trained” or when one has an intense fight-fright-flight emergency response.
  • As the bladder fills, stretch receptors communicate fullness to the brain, causing reflex contraction of the detrusor muscle and relaxation of the internal urethral sphincter.
  • This reflex can be overcome by contraction of the voluntary external urethral sphincter in the deep perineal pouch (if you are toilet trained!), preventing flow of urine in the urethra.
  • Conscious relaxation of the pelvic diaphragm and external urethral sphincter allows urine to flow. When you can’t relax (as in a crowded public restroom), tense muscles and sympathetic closure of the internal urethral sphincter results in an unfortunate inability to micturate.

 

This site has a nice description of neural control of micturation.

  • Superior rectal artery (from inferior mesenteric) and middle rectal artery (from internal iliac).
  • Venous drainage: A submucosal rectal venous plexus drains to the superior rectal vein (portal drainage) and middle rectalveins (systemic drainage = IVC).
  • Split: Upper rectum to inferior mesenteric nodes along aorta; lower rectum to internal iliac and sacral nodes.
  • Sympathetic: From upper lumbar segments of spinal cord to pelvic plexus via the hypogastric nerves—this is vasomotor,but may also relax smooth muscle to inhibit peristalsis and constrict the internal anal sphincter.
  • Parasympathetic: From pelvic splanchnic nerves—stimulates peristalsis; relaxes internal anal sphincter.
  • Afferent: Carry information concerning stretch and fullness to the sacral spinal cord via pelvic splanchnic nerves. Most of the rectum is below the pelvic pain line, so pain is referred to sacral dermatomes and is poorly localized in the pelvic region.
  • The rectum fills slowly during the day, the feces being delivered by peristalsis in the descending and sigmoid colons.
  • The urge to defecate is initiated by mucosal receptors in the ampulla. This induces the relaxation of the internal anal sphincter (smooth muscle) and increases rectal peristalsis.
  • Reflex stimulation of the external anal sphincter (skeletal muscle) resists the pressure produced by peristalsis—maintaining fecal continence.
  • Relaxation of the voluntary sphincter and puborectalis muscle and initiation of the Valsalva maneuver (“bearing down”) with continued peristaltic activity empties the rectum.
  • Posterior to the base of the bladder.
  • The upper blind ends of the vesicles are adjacent to the rectovesical pouch.
  • Just above the prostate, their ducts join the ductus deferentes to form the ejaculatory ducts.
  • Figure 20.24 GRAY’S ANATOMY FOR STUDENTS, FIGURE 5.47.
    This can be confusing, since anatomists and urologists use different terms, and they are often mixed and matched. The passage of the urethra and ejaculatory ducts through the prostate divides it into anatomic lobes and clinical zones.
  • Anterior lobe (isthmus) is anterior to the urethra—also known as the fibromuscular zone. There is no glandular tissue here.
  • Left and right lobes are lateral to the urethra and meet posteriorly in a shallow groove. These lobes together constitute the peripheral zone, the posterior portion of which is palpated in a rectal exam. This zone is the most common location of prostate cancer.
  • Median lobe is the tissue surrounding the ejaculatory ducts. Also called the central zone.
  • The transitional zone is sandwiched between the three zones just described. It encircles the urethra in the core of the prostate, below the bladder. This is the region affected by benign hyperplasia.
  • Figure 20.19 NETTER, ATLAS OF HUMAN ANATOMY, PLATE 341.
    Ovarian ligament (proper ligament of ovary): Ovary to cornu of uterus.
  • Suspensory ligament of the ovary (infundibulopelvic ligament): A peritoneal curtain over the ovarian vessels that extends upward over the pelvic brim.
  • Figure 20.14 GRAY’S ANATOMY FOR STUDENTS, FIGURE 5.54.
    The typical orientation of the uterus is described as anteflexed and anteverted. Flexion refers to orientation of the uterine body with respect to the uterine cervix. Version refers to the orientation of the entire uterus compared to the vagina.
    • When anteflexed, the body of the uterus is bent anteriorly upon the cervix.
    • When anteverted, the entire uterus is tilted forward on the vaginal canal—the uterus and vagina thus have a profile shaped like the number “7” in a lateral view.
  • Parametrium: Outermost, composed of visceral pelvic fascia.
  • Myometrium: Middle layer, thick smooth muscle, branches of the uterine vessels are in this layer.
  • Endometrium: Inner layer, mucous membrane with uterine glands.Undergoes monthly renewal and degeneration—being cyclically prepared by hormones for implantation of the embryo.

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Purely sensory

I
II
VIII

Mainly motor

III
IV
VI
XI
XII

Mixed

V
VII
IX
X

Functions

Olfaction (smell)—special sensory

Skull opening

Olfactory (cribriform) foramina.

Attachments to CNS

Nucleus of origin/destination in CNS

Bipolar neurons of olfactory nerves synapse on secondary olfactory neurons in olfactory bulbs.

Details

Thought question
If the vermis of the cerebellum were affected, what type of signs could a child exhibit?

Review

A pediatric patient has a neuroblastoma associated with the adrenal medulla. This tumor could be related to a pathological disturbance of which of these embryonic structures?

Tap the arrow to view the case.
A 75-year-old gentleman. Felipe Moreno, is brought in by his family because of a 6-month history of progressive difficulty with walking and balance and a 4-month history of urinary incontinence. Further inquiry reveals that, while he was once gregarious and busy with any one of dozens of projects, he now spends his days quietly sitting alone, staring into space.
On a neurologic exam, Felipe generally answers appropriately when asked a question, but only with single words or short sentences without elaboration. If given several tasks in sequence, he will at best complete one of them (motor impersistence). For example, if asked to write a note, fold the paper, put it in an envelope, and seal it, he may simply write one word on the paper.
Felipe cannot rise to a standing position without assistance. As he attempts to walk, his feet appear to be glued to the floor (magnetic gait). Eventually he is able to make wide-based steps, and he also has stiffness and is unable to pivot properly.
A ventriculoperitoneal shunt was placed, and Felipe's gait and urinary incontinence improved markedly, but he still had lingering significant cognitive impairment.
Describe some possible causes of NPH in this patient.
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18. The retroperitoneum (posterior abdominal wall)
20. Pelvic viscera
  • Know this!

    Different parts of the urinary tract come from different embryologic sources:

  • Nephrons

    The excretory units of the kidneys (from intermediate mesoderm)

  • Collecting system

    Collecting ducts through ureters (from mesonephric duct)

  • Urinary bladder and urethra

    (From primitive urogenital sinus)